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 $209.53   9.654%   $229.758   $229.76   $229.75   $229.80  
  Purchase #2 $44.49   3.513%   $46.0529   $46.05   $46.05   $46.10  
  Purchase #3 $21.74   10.454%   $24.0127   $24.01   $24.00   $24.00  
  Purchase #4 $225.32   10.475%   $248.9223   $248.92   $248.90   $248.90  
  Purchase #5 $167.85   11.398%   $186.9815   $186.98   $187.00   $187.00  
  Purchase #6 $10.27   6.715%   $10.9596   $10.96   $10.95   $11.00  
  Purchase #7 $182.83   6.834%   $195.3246   $195.32   $195.30   $195.30  
  7 purchase totals = $862.03       $942.0116   $942.00   $941.95   $942.10