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 $88.91   5.678%   $93.9583   $93.96   $93.95   $94.00  
  Purchase #2 $95.73   8.624%   $103.9858   $103.99   $104.00   $104.00  
  Purchase #3 $88.86   6.277%   $94.4377   $94.44   $94.45   $94.40  
  Purchase #4 $195.40   7.300%   $209.6642   $209.66   $209.65   $209.70  
  Purchase #5 $40.77   11.497%   $45.4573   $45.46   $45.45   $45.50  
  Purchase #6 $241.85   6.788%   $258.2668   $258.27   $258.25   $258.30  
  Purchase #7 $155.68   8.463%   $168.8552   $168.86   $168.85   $168.90  
  7 purchase totals = $907.20       $974.6253   $974.64   $974.60   $974.80