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 $147.51   10.459%   $162.9381   $162.94   $162.95   $162.90  
  Purchase #2 $60.42   11.276%   $67.233   $67.23   $67.25   $67.20  
  Purchase #3 $44.99   4.433%   $46.9844   $46.98   $47.00   $47.00  
  Purchase #4 $86.51   7.649%   $93.1271   $93.13   $93.15   $93.10  
  Purchase #5 $119.94   8.362%   $129.9694   $129.97   $129.95   $130.00  
  Purchase #6 $104.87   5.448%   $110.5833   $110.58   $110.60   $110.60  
  Purchase #7 $209.83   4.436%   $219.1381   $219.14   $219.15   $219.10  
  7 purchase totals = $774.07       $829.9734   $829.97   $830.05   $829.90