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	$55.33	12.774%	$62.3979	$62.40	$62.40	$62.40
Purchase #2	$173.56	6.105%	$184.1558	$184.16	$184.15	$184.20
Purchase #3	$236.30	4.541%	$247.0304	$247.03	$247.05	$247.00
Purchase #4	$180.82	10.856%	$200.4498	$200.45	$200.45	$200.40
Purchase #5	$46.97	11.623%	$52.4293	$52.43	$52.45	$52.40
Purchase #6	$100.39	4.775%	$105.1836	$105.18	$105.20	$105.20
Purchase #7	$7.47	4.514%	$7.8072	$7.81	$7.80	$7.80
7 purchase totals =	$800.84		$859.4540	$859.46	$859.50	$859.40