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 $116.70   8.523%   $126.6463   $126.65   $126.65   $126.60  
  Purchase #2 $212.59   13.455%   $241.194   $241.19   $241.20   $241.20  
  Purchase #3 $66.92   6.339%   $71.1621   $71.16   $71.15   $71.20  
  Purchase #4 $225.90   4.283%   $235.5753   $235.58   $235.60   $235.60  
  Purchase #5 $106.94   11.531%   $119.2713   $119.27   $119.25   $119.30  
  Purchase #6 $224.38   8.764%   $244.0447   $244.04   $244.05   $244.00  
  Purchase #7 $164.45   3.681%   $170.5034   $170.50   $170.50   $170.50  
  7 purchase totals = $1,117.88       $1,208.3971   $1,208.39   $1,208.40   $1,208.40