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	$208.41	10.556%	$230.4098	$230.41	$230.40	$230.40
Purchase #2	$145.89	9.578%	$159.8633	$159.86	$159.85	$159.90
Purchase #3	$239.50	12.501%	$269.4399	$269.44	$269.45	$269.40
Purchase #4	$119.86	5.314%	$126.2294	$126.23	$126.25	$126.20
Purchase #5	$99.85	7.289%	$107.1281	$107.13	$107.15	$107.10
Purchase #6	$104.36	7.169%	$111.8416	$111.84	$111.85	$111.80
Purchase #7	$130.83	11.154%	$145.4228	$145.42	$145.40	$145.40
7 purchase totals =	$1,048.70		$1,150.3349	$1,150.33	$1,150.35	$1,150.20