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 $91.60   3.674%   $94.9654   $94.97   $94.95   $95.00  
  Purchase #2 $225.54   11.477%   $251.4252   $251.43   $251.45   $251.40  
  Purchase #3 $171.74   10.682%   $190.0853   $190.09   $190.10   $190.10  
  Purchase #4 $39.42   11.218%   $43.8421   $43.84   $43.85   $43.80  
  Purchase #5 $89.60   7.612%   $96.4204   $96.42   $96.40   $96.40  
  Purchase #6 $48.84   4.476%   $51.0261   $51.03   $51.05   $51.00  
  Purchase #7 $143.93   6.671%   $153.5316   $153.53   $153.55   $153.50  
  7 purchase totals = $810.67       $881.2961   $881.31   $881.35   $881.20