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 $206.65   4.852%   $216.6767   $216.68   $216.70   $216.70  
  Purchase #2 $205.34   9.404%   $224.6502   $224.65   $224.65   $224.70  
  Purchase #3 $48.28   8.321%   $52.2974   $52.30   $52.30   $52.30  
  Purchase #4 $96.85   11.124%   $107.6236   $107.62   $107.60   $107.60  
  Purchase #5 $84.56   8.826%   $92.0233   $92.02   $92.00   $92.00  
  Purchase #6 $102.93   11.296%   $114.557   $114.56   $114.55   $114.60  
  Purchase #7 $23.41   4.596%   $24.4859   $24.49   $24.50   $24.50  
  7 purchase totals = $768.02       $832.3141   $832.32   $832.30   $832.40