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 $75.35   9.694%   $82.6544   $82.65   $82.65   $82.70  
  Purchase #2 $213.74   5.105%   $224.6514   $224.65   $224.65   $224.70  
  Purchase #3 $8.27   7.240%   $8.8687   $8.87   $8.85   $8.90  
  Purchase #4 $219.64   4.561%   $229.6578   $229.66   $229.65   $229.70  
  Purchase #5 $182.90   9.116%   $199.5732   $199.57   $199.55   $199.60  
  Purchase #6 $23.31   9.104%   $25.4321   $25.43   $25.45   $25.40  
  Purchase #7 $244.98   11.539%   $273.2482   $273.25   $273.25   $273.20  
  7 purchase totals = $968.19       $1,044.0858   $1,044.08   $1,044.05   $1,044.20