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	$173.33	10.571%	$191.6527	$191.65	$191.65	$191.70
Purchase #2	$56.66	12.603%	$63.8009	$63.80	$63.80	$63.80
Purchase #3	$175.45	7.526%	$188.6544	$188.65	$188.65	$188.70
Purchase #4	$10.66	7.628%	$11.4731	$11.47	$11.45	$11.50
Purchase #5	$168.54	12.820%	$190.1468	$190.15	$190.15	$190.10
Purchase #6	$32.29	11.117%	$35.8797	$35.88	$35.90	$35.90
Purchase #7	$157.54	3.255%	$162.6679	$162.67	$162.65	$162.70
7 purchase totals =	$774.47		$844.2755	$844.27	$844.25	$844.40