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 $69.36   10.528%   $76.6622   $76.66   $76.65   $76.70  
  Purchase #2 $204.28   10.774%   $226.2891   $226.29   $226.30   $226.30  
  Purchase #3 $178.96   11.642%   $199.7945   $199.79   $199.80   $199.80  
  Purchase #4 $78.86   7.578%   $84.836   $84.84   $84.85   $84.80  
  Purchase #5 $102.70   4.728%   $107.5557   $107.56   $107.55   $107.60  
  Purchase #6 $102.34   3.460%   $105.881   $105.88   $105.90   $105.90  
  Purchase #7 $116.44   7.573%   $125.258   $125.26   $125.25   $125.30  
  7 purchase totals = $852.94       $926.2765   $926.28   $926.30   $926.40