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 $69.61   10.111%   $76.6483   $76.65   $76.65   $76.60  
  Purchase #2 $139.49   11.530%   $155.5732   $155.57   $155.55   $155.60  
  Purchase #3 $247.34   6.398%   $263.1648   $263.16   $263.15   $263.20  
  Purchase #4 $158.62   10.449%   $175.1942   $175.19   $175.20   $175.20  
  Purchase #5 $96.69   8.349%   $104.7626   $104.76   $104.75   $104.80  
  Purchase #6 $133.44   13.351%   $151.2556   $151.26   $151.25   $151.30  
  Purchase #7 $32.33   5.731%   $34.1828   $34.18   $34.20   $34.20  
  7 purchase totals = $877.52       $960.7815   $960.77   $960.75   $960.90