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 $62.87   10.118%   $69.2312   $69.23   $69.25   $69.20  
  Purchase #2 $108.30   8.693%   $117.7145   $117.71   $117.70   $117.70  
  Purchase #3 $113.81   6.199%   $120.8651   $120.87   $120.85   $120.90  
  Purchase #4 $18.29   12.539%   $20.5834   $20.58   $20.60   $20.60  
  Purchase #5 $180.38   8.216%   $195.2   $195.20   $195.20   $195.20  
  Purchase #6 $87.79   3.438%   $90.8082   $90.81   $90.80   $90.80  
  Purchase #7 $115.50   3.442%   $119.4755   $119.48   $119.50   $119.50  
  7 purchase totals = $686.94       $733.8779   $733.88   $733.90   $733.90