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	$190.27	4.849%	$199.4962	$199.50	$199.50	$199.50
Purchase #2	$148.87	13.173%	$168.4806	$168.48	$168.50	$168.50
Purchase #3	$123.53	11.288%	$137.4741	$137.47	$137.45	$137.50
Purchase #4	$173.49	3.672%	$179.8606	$179.86	$179.85	$179.90
Purchase #5	$139.87	10.590%	$154.6822	$154.68	$154.70	$154.70
Purchase #6	$22.52	13.104%	$25.471	$25.47	$25.45	$25.50
Purchase #7	$239.65	9.442%	$262.2778	$262.28	$262.30	$262.30
7 purchase totals =	$1,038.20		$1,127.7425	$1,127.74	$1,127.75	$1,127.90