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 $92.97   4.581%   $97.229   $97.23   $97.25   $97.20  
  Purchase #2 $204.95   13.320%   $232.2493   $232.25   $232.25   $232.20  
  Purchase #3 $11.73   11.513%   $13.0805   $13.08   $13.10   $13.10  
  Purchase #4 $246.71   12.484%   $277.5093   $277.51   $277.50   $277.50  
  Purchase #5 $169.38   8.821%   $184.321   $184.32   $184.30   $184.30  
  Purchase #6 $109.60   7.422%   $117.7345   $117.73   $117.75   $117.70  
  Purchase #7 $64.49   7.817%   $69.5312   $69.53   $69.55   $69.50  
  7 purchase totals = $899.83       $991.6548   $991.65   $991.70   $991.50