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 $105.78   8.202%   $114.4561   $114.46   $114.45   $114.50  
  Purchase #2 $26.26   9.116%   $28.6539   $28.65   $28.65   $28.70  
  Purchase #3 $176.52   10.442%   $194.9522   $194.95   $194.95   $195.00  
  Purchase #4 $197.95   5.296%   $208.4334   $208.43   $208.45   $208.40  
  Purchase #5 $185.33   13.492%   $210.3347   $210.33   $210.35   $210.30  
  Purchase #6 $101.57   9.634%   $111.3553   $111.36   $111.35   $111.40  
  Purchase #7 $126.91   13.411%   $143.9299   $143.93   $143.95   $143.90  
  7 purchase totals = $920.32       $1,012.1155   $1,012.11   $1,012.15   $1,012.20