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 $61.63   5.738%   $65.1663   $65.17   $65.15   $65.20  
  Purchase #2 $156.69   8.453%   $169.935   $169.94   $169.95   $169.90  
  Purchase #3 $247.83   4.318%   $258.5313   $258.53   $258.55   $258.50  
  Purchase #4 $211.84   4.198%   $220.733   $220.73   $220.75   $220.70  
  Purchase #5 $109.46   10.476%   $120.927   $120.93   $120.95   $120.90  
  Purchase #6 $166.51   4.864%   $174.609   $174.61   $174.60   $174.60  
  Purchase #7 $21.27   9.802%   $23.3549   $23.35   $23.35   $23.40  
  7 purchase totals = $975.23       $1,033.2565   $1,033.26   $1,033.30   $1,033.20