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 $216.58   7.146%   $232.0568   $232.06   $232.05   $232.10  
  Purchase #2 $20.59   7.591%   $22.153   $22.15   $22.15   $22.20  
  Purchase #3 $132.31   4.264%   $137.9517   $137.95   $137.95   $138.00  
  Purchase #4 $68.41   9.257%   $74.7427   $74.74   $74.75   $74.70  
  Purchase #5 $239.28   9.343%   $261.6359   $261.64   $261.65   $261.60  
  Purchase #6 $160.52   6.360%   $170.7291   $170.73   $170.75   $170.70  
  Purchase #7 $63.87   3.546%   $66.1348   $66.13   $66.15   $66.10  
  7 purchase totals = $901.56       $965.4040   $965.40   $965.45   $965.40