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	$212.35	13.598%	$241.2254	$241.23	$241.25	$241.20
Purchase #2	$249.41	11.429%	$277.9151	$277.92	$277.90	$277.90
Purchase #3	$222.49	4.766%	$233.0939	$233.09	$233.10	$233.10
Purchase #4	$110.76	7.808%	$119.4081	$119.41	$119.40	$119.40
Purchase #5	$66.72	9.789%	$73.2512	$73.25	$73.25	$73.30
Purchase #6	$75.85	10.393%	$83.7331	$83.73	$83.75	$83.70
Purchase #7	$244.65	4.598%	$255.899	$255.90	$255.90	$255.90
7 purchase totals =	$1,182.23		$1,284.5258	$1,284.53	$1,284.55	$1,284.50