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 $87.82   8.433%   $95.2259   $95.23   $95.25   $95.20  
  Purchase #2 $43.81   6.253%   $46.5494   $46.55   $46.55   $46.50  
  Purchase #3 $65.70   13.290%   $74.4315   $74.43   $74.45   $74.40  
  Purchase #4 $237.66   3.420%   $245.788   $245.79   $245.80   $245.80  
  Purchase #5 $78.98   7.119%   $84.6026   $84.60   $84.60   $84.60  
  Purchase #6 $97.61   4.841%   $102.3353   $102.34   $102.35   $102.30  
  Purchase #7 $110.70   5.172%   $116.4254   $116.43   $116.45   $116.40  
  7 purchase totals = $722.28       $765.3581   $765.37   $765.45   $765.20