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	$198.50	11.677%	$221.6788	$221.68	$221.70	$221.70
Purchase #2	$26.57	3.563%	$27.5167	$27.52	$27.50	$27.50
Purchase #3	$194.77	11.594%	$217.3516	$217.35	$217.35	$217.40
Purchase #4	$172.78	3.538%	$178.893	$178.89	$178.90	$178.90
Purchase #5	$175.31	6.414%	$186.5544	$186.55	$186.55	$186.60
Purchase #6	$80.57	10.662%	$89.1604	$89.16	$89.15	$89.20
Purchase #7	$167.66	6.385%	$178.3651	$178.37	$178.35	$178.40
7 purchase totals =	$1,016.16		$1,099.5200	$1,099.52	$1,099.50	$1,099.70