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 $62.79   5.163%   $66.0318   $66.03   $66.05   $66.00  
  Purchase #2 $106.80   5.273%   $112.4316   $112.43   $112.45   $112.40  
  Purchase #3 $222.72   5.493%   $234.954   $234.95   $234.95   $235.00  
  Purchase #4 $17.43   3.722%   $18.0787   $18.08   $18.10   $18.10  
  Purchase #5 $204.72   7.536%   $220.1477   $220.15   $220.15   $220.10  
  Purchase #6 $134.39   5.726%   $142.0852   $142.09   $142.10   $142.10  
  Purchase #7 $132.38   6.475%   $140.9516   $140.95   $140.95   $141.00  
  7 purchase totals = $881.23       $934.6806   $934.68   $934.75   $934.70