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 $196.34   9.865%   $215.7089   $215.71   $215.70   $215.70  
  Purchase #2 $100.29   7.186%   $107.4968   $107.50   $107.50   $107.50  
  Purchase #3 $114.50   6.369%   $121.7925   $121.79   $121.80   $121.80  
  Purchase #4 $246.90   6.635%   $263.2818   $263.28   $263.30   $263.30  
  Purchase #5 $167.60   9.855%   $184.117   $184.12   $184.10   $184.10  
  Purchase #6 $94.43   11.581%   $105.3659   $105.37   $105.35   $105.40  
  Purchase #7 $58.27   11.590%   $65.0235   $65.02   $65.00   $65.00  
  7 purchase totals = $978.33       $1,062.7864   $1,062.79   $1,062.75   $1,062.80