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	$187.69	9.495%	$205.5112	$205.51	$205.50	$205.50
Purchase #2	$207.89	5.693%	$219.7252	$219.73	$219.75	$219.70
Purchase #3	$92.88	13.106%	$105.0529	$105.05	$105.05	$105.10
Purchase #4	$60.56	10.187%	$66.7292	$66.73	$66.75	$66.70
Purchase #5	$141.98	11.373%	$158.1274	$158.13	$158.15	$158.10
Purchase #6	$159.29	13.344%	$180.5457	$180.55	$180.55	$180.50
Purchase #7	$175.41	5.690%	$185.3908	$185.39	$185.40	$185.40
7 purchase totals =	$1,025.70		$1,121.0824	$1,121.09	$1,121.15	$1,121.00