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 $116.40   8.840%   $126.6898   $126.69   $126.70   $126.70  
  Purchase #2 $225.61   9.193%   $246.3503   $246.35   $246.35   $246.40  
  Purchase #3 $9.31   5.660%   $9.8369   $9.84   $9.85   $9.80  
  Purchase #4 $23.46   6.596%   $25.0074   $25.01   $25.00   $25.00  
  Purchase #5 $247.54   8.603%   $268.8359   $268.84   $268.85   $268.80  
  Purchase #6 $118.26   11.481%   $131.8374   $131.84   $131.85   $131.80  
  Purchase #7 $131.42   11.138%   $146.0576   $146.06   $146.05   $146.10  
  7 purchase totals = $872.00       $954.6153   $954.63   $954.65   $954.60