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	$104.46	6.746%	$111.5069	$111.51	$111.50	$111.50
Purchase #2	$238.52	9.263%	$260.6141	$260.61	$260.60	$260.60
Purchase #3	$91.72	9.480%	$100.4151	$100.42	$100.40	$100.40
Purchase #4	$247.99	9.824%	$272.3525	$272.35	$272.35	$272.40
Purchase #5	$122.54	5.481%	$129.2564	$129.26	$129.25	$129.30
Purchase #6	$56.80	5.261%	$59.7882	$59.79	$59.80	$59.80
Purchase #7	$149.75	8.344%	$162.2451	$162.25	$162.25	$162.20
7 purchase totals =	$1,011.78		$1,096.1783	$1,096.19	$1,096.15	$1,096.20