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 $54.96   13.858%   $62.5764   $62.58   $62.60   $62.60  
  Purchase #2 $81.87   3.376%   $84.6339   $84.63   $84.65   $84.60  
  Purchase #3 $50.28   4.251%   $52.4174   $52.42   $52.40   $52.40  
  Purchase #4 $217.28   4.494%   $227.0446   $227.04   $227.05   $227.00  
  Purchase #5 $95.55   4.591%   $99.9367   $99.94   $99.95   $99.90  
  Purchase #6 $216.29   11.590%   $241.358   $241.36   $241.35   $241.40  
  Purchase #7 $204.41   11.317%   $227.5431   $227.54   $227.55   $227.50  
  7 purchase totals = $920.64       $995.5101   $995.51   $995.55   $995.40