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 $60.27   5.321%   $63.477   $63.48   $63.50   $63.50  
  Purchase #2 $210.44   4.249%   $219.3816   $219.38   $219.40   $219.40  
  Purchase #3 $89.26   11.784%   $99.7784   $99.78   $99.80   $99.80  
  Purchase #4 $203.95   11.722%   $227.857   $227.86   $227.85   $227.90  
  Purchase #5 $95.75   8.756%   $104.1339   $104.13   $104.15   $104.10  
  Purchase #6 $235.85   5.562%   $248.968   $248.97   $248.95   $249.00  
  Purchase #7 $155.77   7.143%   $166.8967   $166.90   $166.90   $166.90  
  7 purchase totals = $1,051.29       $1,130.4926   $1,130.50   $1,130.55   $1,130.60