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 $90.87   3.452%   $94.0068   $94.01   $94.00   $94.00  
  Purchase #2 $33.76   3.113%   $34.8109   $34.81   $34.80   $34.80  
  Purchase #3 $56.45   6.328%   $60.0222   $60.02   $60.00   $60.00  
  Purchase #4 $64.69   5.735%   $68.4   $68.40   $68.40   $68.40  
  Purchase #5 $140.29   8.198%   $151.791   $151.79   $151.80   $151.80  
  Purchase #6 $190.90   5.807%   $201.9856   $201.99   $202.00   $202.00  
  Purchase #7 $245.27   7.648%   $264.0282   $264.03   $264.05   $264.00  
  7 purchase totals = $822.23       $875.0447   $875.05   $875.05   $875.00