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	$208.42	10.573%	$230.4562	$230.46	$230.45	$230.50
Purchase #2	$63.80	6.165%	$67.7333	$67.73	$67.75	$67.70
Purchase #3	$185.92	10.726%	$205.8618	$205.86	$205.85	$205.90
Purchase #4	$127.70	4.618%	$133.5972	$133.60	$133.60	$133.60
Purchase #5	$241.87	5.655%	$255.5477	$255.55	$255.55	$255.50
Purchase #6	$244.72	9.714%	$268.4921	$268.49	$268.50	$268.50
Purchase #7	$158.78	6.131%	$168.5148	$168.51	$168.50	$168.50
7 purchase totals =	$1,231.21		$1,330.2031	$1,330.20	$1,330.20	$1,330.20