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 $72.84   5.663%   $76.9649   $76.96   $76.95   $77.00  
  Purchase #2 $42.92   13.516%   $48.7211   $48.72   $48.70   $48.70  
  Purchase #3 $50.45   7.231%   $54.098   $54.10   $54.10   $54.10  
  Purchase #4 $89.50   8.531%   $97.1352   $97.14   $97.15   $97.10  
  Purchase #5 $124.53   3.611%   $129.0268   $129.03   $129.05   $129.00  
  Purchase #6 $205.78   13.172%   $232.8853   $232.89   $232.90   $232.90  
  Purchase #7 $111.49   9.745%   $122.3547   $122.35   $122.35   $122.40  
  7 purchase totals = $697.51       $761.1860   $761.19   $761.20   $761.20