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 $59.43   5.485%   $62.6897   $62.69   $62.70   $62.70  
  Purchase #2 $145.31   9.661%   $159.3484   $159.35   $159.35   $159.30  
  Purchase #3 $208.33   11.752%   $232.8129   $232.81   $232.80   $232.80  
  Purchase #4 $10.50   11.472%   $11.7046   $11.70   $11.70   $11.70  
  Purchase #5 $236.44   3.342%   $244.3418   $244.34   $244.35   $244.30  
  Purchase #6 $165.36   5.854%   $175.0402   $175.04   $175.05   $175.00  
  Purchase #7 $124.67   3.271%   $128.748   $128.75   $128.75   $128.70  
  7 purchase totals = $950.04       $1,014.6856   $1,014.68   $1,014.70   $1,014.50