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 $244.54   8.498%   $265.321   $265.32   $265.30   $265.30  
  Purchase #2 $214.32   8.795%   $233.1694   $233.17   $233.15   $233.20  
  Purchase #3 $95.73   12.461%   $107.6589   $107.66   $107.65   $107.70  
  Purchase #4 $128.62   13.733%   $146.2834   $146.28   $146.30   $146.30  
  Purchase #5 $48.41   6.228%   $51.425   $51.43   $51.45   $51.40  
  Purchase #6 $184.80   3.527%   $191.3179   $191.32   $191.30   $191.30  
  Purchase #7 $56.80   6.234%   $60.3409   $60.34   $60.35   $60.30  
  7 purchase totals = $973.22       $1,055.5165   $1,055.52   $1,055.50   $1,055.50