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 $119.47   4.697%   $125.0815   $125.08   $125.10   $125.10  
  Purchase #2 $137.40   12.299%   $154.2988   $154.30   $154.30   $154.30  
  Purchase #3 $247.58   5.216%   $260.4938   $260.49   $260.50   $260.50  
  Purchase #4 $8.49   12.805%   $9.5771   $9.58   $9.60   $9.60  
  Purchase #5 $202.82   5.460%   $213.894   $213.89   $213.90   $213.90  
  Purchase #6 $121.43   11.434%   $135.3143   $135.31   $135.30   $135.30  
  Purchase #7 $44.52   3.822%   $46.2216   $46.22   $46.20   $46.20  
  7 purchase totals = $881.71       $944.8811   $944.87   $944.90   $944.90