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	$214.37	3.388%	$221.6329	$221.63	$221.65	$221.60
Purchase #2	$73.32	13.601%	$83.2923	$83.29	$83.30	$83.30
Purchase #3	$230.33	3.550%	$238.5067	$238.51	$238.50	$238.50
Purchase #4	$141.31	9.167%	$154.2639	$154.26	$154.25	$154.30
Purchase #5	$102.64	10.414%	$113.3289	$113.33	$113.35	$113.30
Purchase #6	$233.91	9.285%	$255.6285	$255.63	$255.65	$255.60
Purchase #7	$247.85	3.187%	$255.749	$255.75	$255.75	$255.70
7 purchase totals =	$1,243.73		$1,322.4022	$1,322.40	$1,322.45	$1,322.30