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 $88.46   4.137%   $92.1196   $92.12   $92.10   $92.10  
  Purchase #2 $11.30   10.184%   $12.4508   $12.45   $12.45   $12.50  
  Purchase #3 $215.97   11.583%   $240.9858   $240.99   $241.00   $241.00  
  Purchase #4 $207.34   9.246%   $226.5107   $226.51   $226.50   $226.50  
  Purchase #5 $237.59   8.819%   $258.5431   $258.54   $258.55   $258.50  
  Purchase #6 $113.64   10.452%   $125.5177   $125.52   $125.50   $125.50  
  Purchase #7 $62.52   10.587%   $69.139   $69.14   $69.15   $69.10  
  7 purchase totals = $936.82       $1,025.2667   $1,025.27   $1,025.25   $1,025.20