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 $113.78   9.823%   $124.9566   $124.96   $124.95   $125.00  
  Purchase #2 $73.92   10.266%   $81.5086   $81.51   $81.50   $81.50  
  Purchase #3 $159.53   11.501%   $177.8775   $177.88   $177.90   $177.90  
  Purchase #4 $136.87   7.456%   $147.075   $147.08   $147.10   $147.10  
  Purchase #5 $152.94   11.380%   $170.3446   $170.34   $170.35   $170.30  
  Purchase #6 $95.43   6.842%   $101.9593   $101.96   $101.95   $102.00  
  Purchase #7 $65.61   9.338%   $71.7367   $71.74   $71.75   $71.70  
  7 purchase totals = $798.08       $875.4583   $875.47   $875.50   $875.50