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 $88.63   7.307%   $95.1062   $95.11   $95.10   $95.10  
  Purchase #2 $247.99   4.327%   $258.7205   $258.72   $258.70   $258.70  
  Purchase #3 $31.43   7.296%   $33.7231   $33.72   $33.70   $33.70  
  Purchase #4 $15.76   7.826%   $16.9934   $16.99   $17.00   $17.00  
  Purchase #5 $90.41   6.104%   $95.9286   $95.93   $95.95   $95.90  
  Purchase #6 $104.92   7.308%   $112.5876   $112.59   $112.60   $112.60  
  Purchase #7 $173.84   3.331%   $179.6306   $179.63   $179.65   $179.60  
  7 purchase totals = $752.98       $792.6900   $792.69   $792.70   $792.60