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 $212.68   5.670%   $224.739   $224.74   $224.75   $224.70  
  Purchase #2 $101.69   10.747%   $112.6186   $112.62   $112.60   $112.60  
  Purchase #3 $60.47   12.422%   $67.9816   $67.98   $68.00   $68.00  
  Purchase #4 $203.33   13.738%   $231.2635   $231.26   $231.25   $231.30  
  Purchase #5 $219.60   4.692%   $229.9036   $229.90   $229.90   $229.90  
  Purchase #6 $22.40   4.193%   $23.3392   $23.34   $23.35   $23.30  
  Purchase #7 $157.34   3.783%   $163.2922   $163.29   $163.30   $163.30  
  7 purchase totals = $977.51       $1,053.1377   $1,053.13   $1,053.15   $1,053.10