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 $182.68   7.859%   $197.0368   $197.04   $197.05   $197.00  
  Purchase #2 $72.79   13.236%   $82.4245   $82.42   $82.40   $82.40  
  Purchase #3 $47.56   8.502%   $51.6036   $51.60   $51.60   $51.60  
  Purchase #4 $230.29   4.630%   $240.9524   $240.95   $240.95   $241.00  
  Purchase #5 $149.27   8.789%   $162.3893   $162.39   $162.40   $162.40  
  Purchase #6 $118.52   5.177%   $124.6558   $124.66   $124.65   $124.70  
  Purchase #7 $209.80   8.412%   $227.4484   $227.45   $227.45   $227.40  
  7 purchase totals = $1,010.91       $1,086.5108   $1,086.51   $1,086.50   $1,086.50