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	$30.65	9.834%	$33.6641	$33.66	$33.65	$33.70
Purchase #2	$54.51	13.545%	$61.8934	$61.89	$61.90	$61.90
Purchase #3	$32.58	4.720%	$34.1178	$34.12	$34.10	$34.10
Purchase #4	$89.52	9.714%	$98.216	$98.22	$98.20	$98.20
Purchase #5	$234.42	11.174%	$260.6141	$260.61	$260.60	$260.60
Purchase #6	$144.99	4.188%	$151.0622	$151.06	$151.05	$151.10
Purchase #7	$77.63	6.601%	$82.7544	$82.75	$82.75	$82.80
7 purchase totals =	$664.30		$722.3220	$722.31	$722.25	$722.40