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 $58.89   5.340%   $62.0347   $62.03   $62.05   $62.00  
  Purchase #2 $173.91   10.264%   $191.7601   $191.76   $191.75   $191.80  
  Purchase #3 $132.63   5.145%   $139.4538   $139.45   $139.45   $139.50  
  Purchase #4 $176.88   3.596%   $183.2406   $183.24   $183.25   $183.20  
  Purchase #5 $43.59   11.392%   $48.5558   $48.56   $48.55   $48.60  
  Purchase #6 $216.39   6.872%   $231.2603   $231.26   $231.25   $231.30  
  Purchase #7 $231.77   5.574%   $244.6889   $244.69   $244.70   $244.70  
  7 purchase totals = $1,034.06       $1,100.9942   $1,100.99   $1,101.00   $1,101.10