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 $88.36   8.354%   $95.7416   $95.74   $95.75   $95.70  
  Purchase #2 $162.56   6.759%   $173.5474   $173.55   $173.55   $173.50  
  Purchase #3 $212.43   5.482%   $224.0754   $224.08   $224.10   $224.10  
  Purchase #4 $156.36   12.738%   $176.2771   $176.28   $176.30   $176.30  
  Purchase #5 $101.90   8.827%   $110.8947   $110.89   $110.90   $110.90  
  Purchase #6 $88.68   12.212%   $99.5096   $99.51   $99.50   $99.50  
  Purchase #7 $177.66   9.573%   $194.6674   $194.67   $194.65   $194.70  
  7 purchase totals = $987.95       $1,074.7132   $1,074.72   $1,074.75   $1,074.70