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	$244.76	11.359%	$272.5623	$272.56	$272.55	$272.60
Purchase #2	$220.35	13.638%	$250.4013	$250.40	$250.40	$250.40
Purchase #3	$126.83	3.787%	$131.6331	$131.63	$131.65	$131.60
Purchase #4	$39.29	9.177%	$42.8956	$42.90	$42.90	$42.90
Purchase #5	$108.85	8.795%	$118.4234	$118.42	$118.40	$118.40
Purchase #6	$138.43	3.782%	$143.6654	$143.67	$143.65	$143.70
Purchase #7	$194.69	6.245%	$206.8484	$206.85	$206.85	$206.80
7 purchase totals =	$1,073.20		$1,166.4295	$1,166.43	$1,166.40	$1,166.40