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 $54.34   12.179%   $60.9581   $60.96   $60.95   $61.00  
  Purchase #2 $165.95   11.597%   $185.1952   $185.20   $185.20   $185.20  
  Purchase #3 $26.75   11.287%   $29.7693   $29.77   $29.75   $29.80  
  Purchase #4 $117.42   6.707%   $125.2954   $125.30   $125.30   $125.30  
  Purchase #5 $196.54   11.632%   $219.4015   $219.40   $219.40   $219.40  
  Purchase #6 $85.99   11.178%   $95.602   $95.60   $95.60   $95.60  
  Purchase #7 $205.76   6.288%   $218.6982   $218.70   $218.70   $218.70  
  7 purchase totals = $852.75       $934.9197   $934.93   $934.90   $935.00