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 $182.30   9.460%   $199.5456   $199.55   $199.55   $199.50  
  Purchase #2 $88.53   11.105%   $98.3613   $98.36   $98.35   $98.40  
  Purchase #3 $247.39   6.844%   $264.3214   $264.32   $264.30   $264.30  
  Purchase #4 $21.33   13.852%   $24.2846   $24.28   $24.30   $24.30  
  Purchase #5 $73.36   3.546%   $75.9613   $75.96   $75.95   $76.00  
  Purchase #6 $136.73   8.830%   $148.8033   $148.80   $148.80   $148.80  
  Purchase #7 $194.88   10.557%   $215.4535   $215.45   $215.45   $215.50  
  7 purchase totals = $944.52       $1,026.7310   $1,026.72   $1,026.70   $1,026.80