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 $88.86   6.858%   $94.954   $94.95   $94.95   $95.00  
  Purchase #2 $25.28   9.294%   $27.6295   $27.63   $27.65   $27.60  
  Purchase #3 $149.53   6.540%   $159.3093   $159.31   $159.30   $159.30  
  Purchase #4 $104.62   3.234%   $108.0034   $108.00   $108.00   $108.00  
  Purchase #5 $188.79   5.327%   $198.8468   $198.85   $198.85   $198.80  
  Purchase #6 $206.71   5.261%   $217.585   $217.59   $217.60   $217.60  
  Purchase #7 $88.67   13.839%   $100.941   $100.94   $100.95   $100.90  
  7 purchase totals = $852.46       $907.2690   $907.27   $907.30   $907.20