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	$118.70	9.614%	$130.1118	$130.11	$130.10	$130.10
Purchase #2	$158.28	9.799%	$173.7899	$173.79	$173.80	$173.80
Purchase #3	$120.85	10.294%	$133.2903	$133.29	$133.30	$133.30
Purchase #4	$30.76	13.344%	$34.8646	$34.86	$34.85	$34.90
Purchase #5	$74.79	4.695%	$78.3014	$78.30	$78.30	$78.30
Purchase #6	$53.36	13.114%	$60.3576	$60.36	$60.35	$60.40
Purchase #7	$173.30	13.515%	$196.7215	$196.72	$196.70	$196.70
7 purchase totals =	$730.04		$807.4371	$807.43	$807.40	$807.50