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	$242.89	13.432%	$275.515	$275.52	$275.50	$275.50
Purchase #2	$201.83	4.347%	$210.6036	$210.60	$210.60	$210.60
Purchase #3	$9.67	6.500%	$10.2986	$10.30	$10.30	$10.30
Purchase #4	$190.38	5.155%	$200.1941	$200.19	$200.20	$200.20
Purchase #5	$101.77	8.305%	$110.222	$110.22	$110.20	$110.20
Purchase #6	$169.68	3.475%	$175.5764	$175.58	$175.60	$175.60
Purchase #7	$128.85	12.436%	$144.8738	$144.87	$144.85	$144.90
7 purchase totals =	$1,045.07		$1,127.2835	$1,127.28	$1,127.25	$1,127.30