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	$92.96	12.199%	$104.3002	$104.30	$104.30	$104.30
Purchase #2	$35.95	4.694%	$37.6375	$37.64	$37.65	$37.60
Purchase #3	$154.79	9.628%	$169.6932	$169.69	$169.70	$169.70
Purchase #4	$62.95	13.715%	$71.5836	$71.58	$71.60	$71.60
Purchase #5	$155.49	13.394%	$176.3163	$176.32	$176.30	$176.30
Purchase #6	$74.52	4.761%	$78.0679	$78.07	$78.05	$78.10
Purchase #7	$205.63	7.698%	$221.4594	$221.46	$221.45	$221.50
7 purchase totals =	$782.29		$859.0581	$859.06	$859.05	$859.10