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 $174.61   4.261%   $182.0501   $182.05   $182.05   $182.10  
  Purchase #2 $14.33   3.594%   $14.845   $14.85   $14.85   $14.80  
  Purchase #3 $183.42   5.468%   $193.4494   $193.45   $193.45   $193.40  
  Purchase #4 $241.44   10.168%   $265.9896   $265.99   $266.00   $266.00  
  Purchase #5 $51.97   6.390%   $55.2909   $55.29   $55.30   $55.30  
  Purchase #6 $49.97   12.508%   $56.2202   $56.22   $56.20   $56.20  
  Purchase #7 $244.88   8.128%   $264.7838   $264.78   $264.80   $264.80  
  7 purchase totals = $960.62       $1,032.6290   $1,032.63   $1,032.65   $1,032.60