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 $105.28   8.253%   $113.9688   $113.97   $113.95   $114.00  
  Purchase #2 $217.62   9.321%   $237.9044   $237.90   $237.90   $237.90  
  Purchase #3 $204.27   11.701%   $228.1716   $228.17   $228.15   $228.20  
  Purchase #4 $195.64   7.593%   $210.4949   $210.49   $210.50   $210.50  
  Purchase #5 $19.81   8.839%   $21.561   $21.56   $21.55   $21.60  
  Purchase #6 $55.63   10.267%   $61.3415   $61.34   $61.35   $61.30  
  Purchase #7 $194.76   11.517%   $217.1905   $217.19   $217.20   $217.20  
  7 purchase totals = $993.01       $1,090.6327   $1,090.62   $1,090.60   $1,090.70