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 $111.49   13.113%   $126.1097   $126.11   $126.10   $126.10  
  Purchase #2 $226.38   5.103%   $237.9322   $237.93   $237.95   $237.90  
  Purchase #3 $236.68   11.311%   $263.4509   $263.45   $263.45   $263.50  
  Purchase #4 $237.85   11.818%   $265.9591   $265.96   $265.95   $266.00  
  Purchase #5 $93.60   4.738%   $98.0348   $98.03   $98.05   $98.00  
  Purchase #6 $66.46   7.776%   $71.6279   $71.63   $71.65   $71.60  
  Purchase #7 $41.89   8.644%   $45.511   $45.51   $45.50   $45.50  
  7 purchase totals = $1,014.35       $1,108.6256   $1,108.62   $1,108.65   $1,108.60