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	$98.30	13.375%	$111.4476	$111.45	$111.45	$111.40
Purchase #2	$128.47	4.871%	$134.7278	$134.73	$134.75	$134.70
Purchase #3	$218.47	12.799%	$246.432	$246.43	$246.45	$246.40
Purchase #4	$212.52	5.713%	$224.6613	$224.66	$224.65	$224.70
Purchase #5	$144.43	10.493%	$159.585	$159.59	$159.60	$159.60
Purchase #6	$137.63	12.653%	$155.0443	$155.04	$155.05	$155.00
Purchase #7	$115.89	10.590%	$128.1628	$128.16	$128.15	$128.20
7 purchase totals =	$1,055.71		$1,160.0608	$1,160.06	$1,160.10	$1,160.00