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	$53.33	11.378%	$59.3979	$59.40	$59.40	$59.40
Purchase #2	$94.92	6.152%	$100.7595	$100.76	$100.75	$100.80
Purchase #3	$151.39	4.847%	$158.7279	$158.73	$158.75	$158.70
Purchase #4	$240.29	12.588%	$270.5377	$270.54	$270.55	$270.50
Purchase #5	$176.30	5.255%	$185.5646	$185.56	$185.55	$185.60
Purchase #6	$129.25	8.321%	$140.0049	$140.00	$140.00	$140.00
Purchase #7	$218.80	6.714%	$233.4902	$233.49	$233.50	$233.50
7 purchase totals =	$1,064.28		$1,148.4827	$1,148.48	$1,148.50	$1,148.50