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	$45.48	11.320%	$50.6283	$50.63	$50.65	$50.60
Purchase #2	$28.86	11.435%	$32.1601	$32.16	$32.15	$32.20
Purchase #3	$162.51	13.785%	$184.912	$184.91	$184.90	$184.90
Purchase #4	$99.74	3.683%	$103.4134	$103.41	$103.40	$103.40
Purchase #5	$68.44	12.710%	$77.1387	$77.14	$77.15	$77.10
Purchase #6	$221.44	13.167%	$250.597	$250.60	$250.60	$250.60
Purchase #7	$146.50	4.619%	$153.2668	$153.27	$153.25	$153.30
7 purchase totals =	$772.97		$852.1163	$852.12	$852.10	$852.10