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	$248.26	10.469%	$274.2503	$274.25	$274.25	$274.30
Purchase #2	$230.84	3.407%	$238.7047	$238.70	$238.70	$238.70
Purchase #3	$10.87	3.740%	$11.2765	$11.28	$11.30	$11.30
Purchase #4	$69.46	13.622%	$78.9218	$78.92	$78.90	$78.90
Purchase #5	$84.86	3.823%	$88.1042	$88.10	$88.10	$88.10
Purchase #6	$123.57	12.806%	$139.3944	$139.39	$139.40	$139.40
Purchase #7	$142.49	6.351%	$151.5395	$151.54	$151.55	$151.50
7 purchase totals =	$910.35		$982.1914	$982.18	$982.20	$982.20