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 $181.53   5.741%   $191.9516   $191.95   $191.95   $192.00  
  Purchase #2 $240.97   10.167%   $265.4694   $265.47   $265.45   $265.50  
  Purchase #3 $98.74   13.534%   $112.1035   $112.10   $112.10   $112.10  
  Purchase #4 $200.26   13.743%   $227.7817   $227.78   $227.80   $227.80  
  Purchase #5 $62.42   5.688%   $65.9704   $65.97   $65.95   $66.00  
  Purchase #6 $10.35   4.224%   $10.7872   $10.79   $10.80   $10.80  
  Purchase #7 $88.42   5.543%   $93.3211   $93.32   $93.30   $93.30  
  7 purchase totals = $882.69       $967.3849   $967.38   $967.35   $967.50