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	$99.85	10.135%	$109.9698	$109.97	$109.95	$110.00
Purchase #2	$121.42	4.668%	$127.0879	$127.09	$127.10	$127.10
Purchase #3	$229.40	3.376%	$237.1445	$237.14	$237.15	$237.10
Purchase #4	$106.70	13.252%	$120.8399	$120.84	$120.85	$120.80
Purchase #5	$51.51	3.147%	$53.131	$53.13	$53.15	$53.10
Purchase #6	$250.47	8.644%	$272.1206	$272.12	$272.10	$272.10
Purchase #7	$132.72	9.174%	$144.8957	$144.90	$144.90	$144.90
7 purchase totals =	$992.07		$1,065.1894	$1,065.19	$1,065.20	$1,065.10