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 $196.35   5.272%   $206.7016   $206.70   $206.70   $206.70  
  Purchase #2 $198.65   8.155%   $214.8499   $214.85   $214.85   $214.80  
  Purchase #3 $32.26   3.648%   $33.4368   $33.44   $33.45   $33.40  
  Purchase #4 $217.46   11.594%   $242.6723   $242.67   $242.65   $242.70  
  Purchase #5 $117.43   12.708%   $132.353   $132.35   $132.35   $132.40  
  Purchase #6 $113.77   11.610%   $126.9787   $126.98   $127.00   $127.00  
  Purchase #7 $19.44   4.265%   $20.2691   $20.27   $20.25   $20.30  
  7 purchase totals = $895.36       $977.2614   $977.26   $977.25   $977.30