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 $52.87   8.500%   $57.364   $57.36   $57.35   $57.40  
  Purchase #2 $237.51   10.873%   $263.3345   $263.33   $263.35   $263.30  
  Purchase #3 $41.49   7.497%   $44.6005   $44.60   $44.60   $44.60  
  Purchase #4 $238.45   6.182%   $253.191   $253.19   $253.20   $253.20  
  Purchase #5 $108.39   10.261%   $119.5119   $119.51   $119.50   $119.50  
  Purchase #6 $28.29   13.404%   $32.082   $32.08   $32.10   $32.10  
  Purchase #7 $118.92   5.848%   $125.8744   $125.87   $125.85   $125.90  
  7 purchase totals = $825.92       $895.9583   $895.94   $895.95   $896.00