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	$241.54	11.478%	$269.264	$269.26	$269.25	$269.30
Purchase #2	$52.37	8.215%	$56.6722	$56.67	$56.65	$56.70
Purchase #3	$241.35	7.492%	$259.4319	$259.43	$259.45	$259.40
Purchase #4	$167.53	10.142%	$184.5209	$184.52	$184.50	$184.50
Purchase #5	$217.93	12.364%	$244.8749	$244.87	$244.85	$244.90
Purchase #6	$50.98	8.103%	$55.1109	$55.11	$55.10	$55.10
Purchase #7	$144.40	7.548%	$155.2993	$155.30	$155.30	$155.30
7 purchase totals =	$1,116.10		$1,225.1741	$1,225.16	$1,225.10	$1,225.20