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 $67.95   10.402%   $75.0182   $75.02   $75.00   $75.00  
  Purchase #2 $133.38   13.128%   $150.8901   $150.89   $150.90   $150.90  
  Purchase #3 $145.98   8.676%   $158.6452   $158.65   $158.65   $158.60  
  Purchase #4 $102.82   4.128%   $107.0644   $107.06   $107.05   $107.10  
  Purchase #5 $52.84   13.843%   $60.1546   $60.15   $60.15   $60.20  
  Purchase #6 $126.88   5.586%   $133.9675   $133.97   $133.95   $134.00  
  Purchase #7 $189.80   10.266%   $209.2849   $209.28   $209.30   $209.30  
  7 purchase totals = $819.65       $895.0249   $895.02   $895.00   $895.10