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 $88.29   7.625%   $95.0221   $95.02   $95.00   $95.00  
  Purchase #2 $48.86   4.463%   $51.0406   $51.04   $51.05   $51.00  
  Purchase #3 $148.84   7.142%   $159.4702   $159.47   $159.45   $159.50  
  Purchase #4 $145.56   4.608%   $152.2674   $152.27   $152.25   $152.30  
  Purchase #5 $215.36   4.823%   $225.7468   $225.75   $225.75   $225.70  
  Purchase #6 $162.26   6.584%   $172.9432   $172.94   $172.95   $172.90  
  Purchase #7 $56.43   3.302%   $58.2933   $58.29   $58.30   $58.30  
  7 purchase totals = $865.60       $914.7836   $914.78   $914.75   $914.70