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 $61.25   10.582%   $67.7315   $67.73   $67.75   $67.70  
  Purchase #2 $55.26   8.143%   $59.7598   $59.76   $59.75   $59.80  
  Purchase #3 $161.65   4.254%   $168.5266   $168.53   $168.55   $168.50  
  Purchase #4 $213.43   9.568%   $233.851   $233.85   $233.85   $233.90  
  Purchase #5 $113.37   5.552%   $119.6643   $119.66   $119.65   $119.70  
  Purchase #6 $123.44   10.778%   $136.7444   $136.74   $136.75   $136.70  
  Purchase #7 $225.71   11.536%   $251.7479   $251.75   $251.75   $251.70  
  7 purchase totals = $954.11       $1,038.0255   $1,038.02   $1,038.05   $1,038.00