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	$146.37	9.849%	$160.786	$160.79	$160.80	$160.80
Purchase #2	$66.26	5.105%	$69.6426	$69.64	$69.65	$69.60
Purchase #3	$145.56	7.814%	$156.9341	$156.93	$156.95	$156.90
Purchase #4	$139.62	7.508%	$150.1027	$150.10	$150.10	$150.10
Purchase #5	$55.83	6.186%	$59.2836	$59.28	$59.30	$59.30
Purchase #6	$64.63	12.389%	$72.637	$72.64	$72.65	$72.60
Purchase #7	$237.32	9.681%	$260.2949	$260.29	$260.30	$260.30
7 purchase totals =	$855.59		$929.6809	$929.67	$929.75	$929.60