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 $63.26   5.405%   $66.6792   $66.68   $66.70   $66.70  
  Purchase #2 $121.93   3.271%   $125.9183   $125.92   $125.90   $125.90  
  Purchase #3 $227.51   7.329%   $244.1842   $244.18   $244.20   $244.20  
  Purchase #4 $146.86   3.415%   $151.8753   $151.88   $151.90   $151.90  
  Purchase #5 $250.91   9.540%   $274.8468   $274.85   $274.85   $274.80  
  Purchase #6 $202.25   11.846%   $226.2085   $226.21   $226.20   $226.20  
  Purchase #7 $97.64   7.686%   $105.1446   $105.14   $105.15   $105.10  
  7 purchase totals = $1,110.36       $1,194.8569   $1,194.86   $1,194.90   $1,194.80