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 $112.52   6.304%   $119.6133   $119.61   $119.60   $119.60  
  Purchase #2 $24.57   4.804%   $25.7503   $25.75   $25.75   $25.80  
  Purchase #3 $216.68   12.843%   $244.5082   $244.51   $244.50   $244.50  
  Purchase #4 $135.87   11.411%   $151.3741   $151.37   $151.35   $151.40  
  Purchase #5 $149.36   5.163%   $157.0715   $157.07   $157.05   $157.10  
  Purchase #6 $100.52   13.556%   $114.1465   $114.15   $114.15   $114.10  
  Purchase #7 $197.66   11.447%   $220.2861   $220.29   $220.30   $220.30  
  7 purchase totals = $937.18       $1,032.7500   $1,032.75   $1,032.70   $1,032.80