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	$94.54	11.624%	$105.5293	$105.53	$105.55	$105.50
Purchase #2	$108.50	8.239%	$117.4393	$117.44	$117.45	$117.40
Purchase #3	$152.55	12.779%	$172.0444	$172.04	$172.05	$172.00
Purchase #4	$195.68	4.609%	$204.6989	$204.70	$204.70	$204.70
Purchase #5	$96.70	3.657%	$100.2363	$100.24	$100.25	$100.20
Purchase #6	$186.83	5.389%	$196.8983	$196.90	$196.90	$196.90
Purchase #7	$18.86	4.272%	$19.6657	$19.67	$19.65	$19.70
7 purchase totals =	$853.66		$916.5122	$916.52	$916.55	$916.40