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	$134.65	12.475%	$151.4476	$151.45	$151.45	$151.40
Purchase #2	$109.47	8.346%	$118.6064	$118.61	$118.60	$118.60
Purchase #3	$238.52	3.576%	$247.0495	$247.05	$247.05	$247.00
Purchase #4	$202.50	9.707%	$222.1567	$222.16	$222.15	$222.20
Purchase #5	$89.88	6.246%	$95.4939	$95.49	$95.50	$95.50
Purchase #6	$85.89	12.130%	$96.3085	$96.31	$96.30	$96.30
Purchase #7	$129.82	4.336%	$135.449	$135.45	$135.45	$135.40
7 purchase totals =	$990.73		$1,066.5116	$1,066.52	$1,066.50	$1,066.40