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 $195.71   7.694%   $210.7679   $210.77   $210.75   $210.80  
  Purchase #2 $45.47   4.612%   $47.5671   $47.57   $47.55   $47.60  
  Purchase #3 $60.68   12.478%   $68.2517   $68.25   $68.25   $68.30  
  Purchase #4 $58.28   5.617%   $61.5536   $61.55   $61.55   $61.60  
  Purchase #5 $176.40   5.681%   $186.4213   $186.42   $186.40   $186.40  
  Purchase #6 $165.54   6.188%   $175.7836   $175.78   $175.80   $175.80  
  Purchase #7 $170.36   7.135%   $182.5152   $182.52   $182.50   $182.50  
  7 purchase totals = $872.44       $932.8604   $932.86   $932.80   $933.00