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 $119.61   6.111%   $126.9194   $126.92   $126.90   $126.90  
  Purchase #2 $108.87   12.154%   $122.1021   $122.10   $122.10   $122.10  
  Purchase #3 $199.83   3.635%   $207.0938   $207.09   $207.10   $207.10  
  Purchase #4 $193.64   9.652%   $212.3301   $212.33   $212.35   $212.30  
  Purchase #5 $244.45   4.721%   $255.9905   $255.99   $256.00   $256.00  
  Purchase #6 $241.52   8.153%   $261.2111   $261.21   $261.20   $261.20  
  Purchase #7 $187.89   6.563%   $200.2212   $200.22   $200.20   $200.20  
  7 purchase totals = $1,295.81       $1,385.8682   $1,385.86   $1,385.85   $1,385.80