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	$185.31	8.208%	$200.5202	$200.52	$200.50	$200.50
Purchase #2	$17.66	10.429%	$19.5018	$19.50	$19.50	$19.50
Purchase #3	$205.97	7.423%	$221.2592	$221.26	$221.25	$221.30
Purchase #4	$60.30	11.505%	$67.2375	$67.24	$67.25	$67.20
Purchase #5	$139.46	3.286%	$144.0427	$144.04	$144.05	$144.00
Purchase #6	$30.64	11.475%	$34.1559	$34.16	$34.15	$34.20
Purchase #7	$100.77	8.488%	$109.3234	$109.32	$109.30	$109.30
7 purchase totals =	$740.11		$796.0407	$796.04	$796.00	$796.00