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 $67.29   11.560%   $75.0687   $75.07   $75.05   $75.10  
  Purchase #2 $224.72   7.697%   $242.0167   $242.02   $242.00   $242.00  
  Purchase #3 $131.50   10.744%   $145.6284   $145.63   $145.65   $145.60  
  Purchase #4 $212.72   10.763%   $235.6151   $235.62   $235.60   $235.60  
  Purchase #5 $102.68   10.516%   $113.4778   $113.48   $113.50   $113.50  
  Purchase #6 $120.81   12.183%   $135.5283   $135.53   $135.55   $135.50  
  Purchase #7 $6.47   8.706%   $7.0333   $7.03   $7.05   $7.00  
  7 purchase totals = $866.19       $954.3683   $954.38   $954.40   $954.30