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	$111.39	5.183%	$117.1633	$117.16	$117.15	$117.20
Purchase #2	$231.75	5.761%	$245.1011	$245.10	$245.10	$245.10
Purchase #3	$54.99	7.654%	$59.1989	$59.20	$59.20	$59.20
Purchase #4	$56.78	6.685%	$60.5757	$60.58	$60.60	$60.60
Purchase #5	$91.26	10.642%	$100.9719	$100.97	$100.95	$101.00
Purchase #6	$79.32	13.667%	$90.1607	$90.16	$90.15	$90.20
Purchase #7	$147.79	3.325%	$152.704	$152.70	$152.70	$152.70
7 purchase totals =	$773.28		$825.8756	$825.87	$825.85	$826.00