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 $212.28   10.191%   $233.9135   $233.91   $233.90   $233.90  
  Purchase #2 $245.95   7.229%   $263.7297   $263.73   $263.75   $263.70  
  Purchase #3 $170.98   13.615%   $194.2589   $194.26   $194.25   $194.30  
  Purchase #4 $107.82   11.171%   $119.8646   $119.86   $119.85   $119.90  
  Purchase #5 $86.29   9.680%   $94.6429   $94.64   $94.65   $94.60  
  Purchase #6 $93.63   10.313%   $103.2861   $103.29   $103.30   $103.30  
  Purchase #7 $19.63   13.760%   $22.3311   $22.33   $22.35   $22.30  
  7 purchase totals = $936.58       $1,032.0268   $1,032.02   $1,032.05   $1,032.00