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	$32.27	8.137%	$34.8958	$34.90	$34.90	$34.90
Purchase #2	$138.88	9.815%	$152.5111	$152.51	$152.50	$152.50
Purchase #3	$100.65	6.410%	$107.1017	$107.10	$107.10	$107.10
Purchase #4	$212.33	13.745%	$241.5148	$241.51	$241.50	$241.50
Purchase #5	$243.38	3.467%	$251.818	$251.82	$251.80	$251.80
Purchase #6	$140.60	12.499%	$158.1736	$158.17	$158.15	$158.20
Purchase #7	$243.77	10.413%	$269.1538	$269.15	$269.15	$269.20
7 purchase totals =	$1,111.88		$1,215.1688	$1,215.16	$1,215.10	$1,215.20