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 $216.41   9.830%   $237.6831   $237.68   $237.70   $237.70  
  Purchase #2 $81.39   13.598%   $92.4574   $92.46   $92.45   $92.50  
  Purchase #3 $67.47   7.666%   $72.6423   $72.64   $72.65   $72.60  
  Purchase #4 $195.54   13.377%   $221.6974   $221.70   $221.70   $221.70  
  Purchase #5 $200.68   12.237%   $225.2372   $225.24   $225.25   $225.20  
  Purchase #6 $249.93   5.729%   $264.2485   $264.25   $264.25   $264.20  
  Purchase #7 $202.51   4.697%   $212.0219   $212.02   $212.00   $212.00  
  7 purchase totals = $1,213.93       $1,325.9878   $1,325.99   $1,326.00   $1,325.90