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 $59.96   9.260%   $65.5123   $65.51   $65.50   $65.50  
  Purchase #2 $191.37   4.309%   $199.6161   $199.62   $199.60   $199.60  
  Purchase #3 $175.97   13.591%   $199.8861   $199.89   $199.90   $199.90  
  Purchase #4 $75.84   4.277%   $79.0837   $79.08   $79.10   $79.10  
  Purchase #5 $159.92   6.686%   $170.6123   $170.61   $170.60   $170.60  
  Purchase #6 $182.56   8.733%   $198.503   $198.50   $198.50   $198.50  
  Purchase #7 $30.82   4.789%   $32.296   $32.30   $32.30   $32.30  
  7 purchase totals = $876.44       $945.5095   $945.51   $945.50   $945.50