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	$158.89	8.271%	$172.0318	$172.03	$172.05	$172.00
Purchase #2	$137.74	6.116%	$146.1642	$146.16	$146.15	$146.20
Purchase #3	$219.80	7.573%	$236.4455	$236.45	$236.45	$236.40
Purchase #4	$94.80	10.829%	$105.0659	$105.07	$105.05	$105.10
Purchase #5	$30.39	3.833%	$31.5548	$31.55	$31.55	$31.60
Purchase #6	$150.77	12.434%	$169.5167	$169.52	$169.50	$169.50
Purchase #7	$32.90	6.467%	$35.0276	$35.03	$35.05	$35.00
7 purchase totals =	$825.29		$895.8065	$895.81	$895.80	$895.80