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	$229.71	11.292%	$255.6489	$255.65	$255.65	$255.60
Purchase #2	$188.50	11.191%	$209.595	$209.60	$209.60	$209.60
Purchase #3	$46.90	6.144%	$49.7815	$49.78	$49.80	$49.80
Purchase #4	$194.27	11.633%	$216.8694	$216.87	$216.85	$216.90
Purchase #5	$20.60	4.434%	$21.5134	$21.51	$21.50	$21.50
Purchase #6	$88.31	3.482%	$91.385	$91.39	$91.40	$91.40
Purchase #7	$194.64	10.180%	$214.4544	$214.45	$214.45	$214.50
7 purchase totals =	$962.93		$1,059.2476	$1,059.25	$1,059.25	$1,059.30