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 $113.52   4.839%   $119.0132   $119.01   $119.00   $119.00  
  Purchase #2 $225.92   8.479%   $245.0758   $245.08   $245.10   $245.10  
  Purchase #3 $74.36   4.638%   $77.8088   $77.81   $77.80   $77.80  
  Purchase #4 $65.69   4.283%   $68.5035   $68.50   $68.50   $68.50  
  Purchase #5 $44.28   5.641%   $46.7778   $46.78   $46.80   $46.80  
  Purchase #6 $159.94   13.127%   $180.9353   $180.94   $180.95   $180.90  
  Purchase #7 $17.27   12.283%   $19.3913   $19.39   $19.40   $19.40  
  7 purchase totals = $700.98       $757.5057   $757.51   $757.55   $757.50