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	$65.35	3.534%	$67.6595	$67.66	$67.65	$67.70
Purchase #2	$240.30	4.380%	$250.8251	$250.83	$250.85	$250.80
Purchase #3	$157.27	9.720%	$172.5566	$172.56	$172.55	$172.60
Purchase #4	$238.58	7.578%	$256.6596	$256.66	$256.65	$256.70
Purchase #5	$131.48	11.151%	$146.1413	$146.14	$146.15	$146.10
Purchase #6	$91.70	7.683%	$98.7453	$98.75	$98.75	$98.70
Purchase #7	$10.45	11.702%	$11.6729	$11.67	$11.65	$11.70
7 purchase totals =	$935.13		$1,004.2603	$1,004.27	$1,004.25	$1,004.30