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 $92.46   3.594%   $95.783   $95.78   $95.80   $95.80  
  Purchase #2 $158.29   13.842%   $180.2005   $180.20   $180.20   $180.20  
  Purchase #3 $243.93   8.577%   $264.8519   $264.85   $264.85   $264.90  
  Purchase #4 $146.51   9.544%   $160.4929   $160.49   $160.50   $160.50  
  Purchase #5 $176.85   5.311%   $186.2425   $186.24   $186.25   $186.20  
  Purchase #6 $174.70   11.788%   $195.2936   $195.29   $195.30   $195.30  
  Purchase #7 $132.48   9.167%   $144.6244   $144.62   $144.60   $144.60  
  7 purchase totals = $1,125.22       $1,227.4888   $1,227.47   $1,227.50   $1,227.50