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 $59.78   8.776%   $65.0263   $65.03   $65.05   $65.00  
  Purchase #2 $215.87   12.241%   $242.2946   $242.29   $242.30   $242.30  
  Purchase #3 $195.78   10.359%   $216.0609   $216.06   $216.05   $216.10  
  Purchase #4 $230.93   5.676%   $244.0376   $244.04   $244.05   $244.00  
  Purchase #5 $52.49   3.555%   $54.356   $54.36   $54.35   $54.40  
  Purchase #6 $116.95   9.554%   $128.1234   $128.12   $128.10   $128.10  
  Purchase #7 $104.41   7.677%   $112.4256   $112.43   $112.45   $112.40  
  7 purchase totals = $976.21       $1,062.3244   $1,062.33   $1,062.35   $1,062.30