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 $214.84   6.761%   $229.3653   $229.37   $229.35   $229.40  
  Purchase #2 $183.74   7.336%   $197.2192   $197.22   $197.20   $197.20  
  Purchase #3 $64.88   11.207%   $72.1511   $72.15   $72.15   $72.20  
  Purchase #4 $32.47   8.377%   $35.19   $35.19   $35.20   $35.20  
  Purchase #5 $191.32   12.251%   $214.7586   $214.76   $214.75   $214.80  
  Purchase #6 $170.74   11.602%   $190.5493   $190.55   $190.55   $190.50  
  Purchase #7 $225.26   5.333%   $237.2731   $237.27   $237.25   $237.30  
  7 purchase totals = $1,083.25       $1,176.5066   $1,176.51   $1,176.45   $1,176.60