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 $110.64   13.658%   $125.7512   $125.75   $125.75   $125.80  
  Purchase #2 $238.28   9.546%   $261.0262   $261.03   $261.05   $261.00  
  Purchase #3 $48.74   5.241%   $51.2945   $51.29   $51.30   $51.30  
  Purchase #4 $248.89   6.622%   $265.3715   $265.37   $265.35   $265.40  
  Purchase #5 $109.35   13.337%   $123.934   $123.93   $123.95   $123.90  
  Purchase #6 $232.27   9.146%   $253.5134   $253.51   $253.50   $253.50  
  Purchase #7 $84.96   11.146%   $94.4296   $94.43   $94.45   $94.40  
  7 purchase totals = $1,073.13       $1,175.3204   $1,175.31   $1,175.35   $1,175.30