Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $198.42   10.347%   $218.9505   $218.95   $218.95   $219.00  
  Purchase #2 $169.93   11.321%   $189.1678   $189.17   $189.15   $189.20  
  Purchase #3 $178.64   13.406%   $202.5885   $202.59   $202.60   $202.60  
  Purchase #4 $235.90   11.796%   $263.7268   $263.73   $263.75   $263.70  
  Purchase #5 $194.78   9.353%   $212.9978   $213.00   $213.00   $213.00  
  Purchase #6 $114.27   11.406%   $127.3036   $127.30   $127.30   $127.30  
  Purchase #7 $175.49   6.571%   $187.0214   $187.02   $187.00   $187.00  
  7 purchase totals = $1,267.43       $1,401.7564   $1,401.76   $1,401.75   $1,401.80