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 $176.45   10.829%   $195.5578   $195.56   $195.55   $195.60  
  Purchase #2 $213.77   10.605%   $236.4403   $236.44   $236.45   $236.40  
  Purchase #3 $207.33   4.216%   $216.071   $216.07   $216.05   $216.10  
  Purchase #4 $237.25   9.798%   $260.4958   $260.50   $260.50   $260.50  
  Purchase #5 $219.78   6.220%   $233.4503   $233.45   $233.45   $233.50  
  Purchase #6 $219.29   8.176%   $237.2192   $237.22   $237.20   $237.20  
  Purchase #7 $184.82   4.561%   $193.2496   $193.25   $193.25   $193.20  
  7 purchase totals = $1,458.69       $1,572.4840   $1,572.49   $1,572.45   $1,572.50