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	$217.83	5.345%	$229.473	$229.47	$229.45	$229.50
Purchase #2	$122.46	13.118%	$138.5243	$138.52	$138.50	$138.50
Purchase #3	$137.54	3.713%	$142.6469	$142.65	$142.65	$142.60
Purchase #4	$97.75	10.222%	$107.742	$107.74	$107.75	$107.70
Purchase #5	$241.58	5.319%	$254.4296	$254.43	$254.45	$254.40
Purchase #6	$85.43	4.632%	$89.3871	$89.39	$89.40	$89.40
Purchase #7	$114.81	7.543%	$123.4701	$123.47	$123.45	$123.50
7 purchase totals =	$1,017.40		$1,085.6730	$1,085.67	$1,085.65	$1,085.60