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	$101.27	10.345%	$111.7464	$111.75	$111.75	$111.70
Purchase #2	$63.25	13.475%	$71.7729	$71.77	$71.75	$71.80
Purchase #3	$30.60	12.665%	$34.4755	$34.48	$34.50	$34.50
Purchase #4	$191.57	6.814%	$204.6236	$204.62	$204.60	$204.60
Purchase #5	$142.83	13.732%	$162.4434	$162.44	$162.45	$162.40
Purchase #6	$49.56	8.271%	$53.6591	$53.66	$53.65	$53.70
Purchase #7	$42.93	7.420%	$46.1154	$46.12	$46.10	$46.10
7 purchase totals =	$622.01		$684.8363	$684.84	$684.80	$684.80