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	$241.77	9.504%	$264.7478	$264.75	$264.75	$264.70
Purchase #2	$93.32	12.420%	$104.9103	$104.91	$104.90	$104.90
Purchase #3	$202.27	4.352%	$211.0728	$211.07	$211.05	$211.10
Purchase #4	$118.72	11.294%	$132.1282	$132.13	$132.15	$132.10
Purchase #5	$103.98	8.792%	$113.1219	$113.12	$113.10	$113.10
Purchase #6	$168.85	3.707%	$175.1093	$175.11	$175.10	$175.10
Purchase #7	$117.98	7.813%	$127.1978	$127.20	$127.20	$127.20
7 purchase totals =	$1,046.89		$1,128.2881	$1,128.29	$1,128.25	$1,128.20