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 $67.26   3.179%   $69.3982   $69.40   $69.40   $69.40  
  Purchase #2 $97.81   4.745%   $102.4511   $102.45   $102.45   $102.50  
  Purchase #3 $153.95   10.671%   $170.378   $170.38   $170.40   $170.40  
  Purchase #4 $206.69   3.336%   $213.5852   $213.59   $213.60   $213.60  
  Purchase #5 $13.82   11.167%   $15.3633   $15.36   $15.35   $15.40  
  Purchase #6 $203.47   11.236%   $226.3319   $226.33   $226.35   $226.30  
  Purchase #7 $190.65   12.476%   $214.4355   $214.44   $214.45   $214.40  
  7 purchase totals = $933.65       $1,011.9432   $1,011.95   $1,012.00   $1,012.00