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 $23.41   3.374%   $24.1999   $24.20   $24.20   $24.20  
  Purchase #2 $236.99   11.658%   $264.6183   $264.62   $264.60   $264.60  
  Purchase #3 $84.91   12.741%   $95.7284   $95.73   $95.75   $95.70  
  Purchase #4 $151.55   12.757%   $170.8832   $170.88   $170.90   $170.90  
  Purchase #5 $85.90   11.521%   $95.7965   $95.80   $95.80   $95.80  
  Purchase #6 $120.96   13.759%   $137.6029   $137.60   $137.60   $137.60  
  Purchase #7 $215.57   4.784%   $225.8829   $225.88   $225.90   $225.90  
  7 purchase totals = $919.29       $1,014.7121   $1,014.71   $1,014.75   $1,014.70