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	$146.51	10.125%	$161.3441	$161.34	$161.35	$161.30
Purchase #2	$224.84	8.802%	$244.6304	$244.63	$244.65	$244.60
Purchase #3	$240.49	11.707%	$268.6442	$268.64	$268.65	$268.60
Purchase #4	$129.41	10.701%	$143.2582	$143.26	$143.25	$143.30
Purchase #5	$51.56	11.376%	$57.4255	$57.43	$57.45	$57.40
Purchase #6	$99.41	6.175%	$105.5486	$105.55	$105.55	$105.50
Purchase #7	$206.97	4.121%	$215.4992	$215.50	$215.50	$215.50
7 purchase totals =	$1,099.19		$1,196.3502	$1,196.35	$1,196.40	$1,196.20