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	$50.51	8.764%	$54.9367	$54.94	$54.95	$54.90
Purchase #2	$122.74	3.707%	$127.29	$127.29	$127.30	$127.30
Purchase #3	$202.73	8.475%	$219.9114	$219.91	$219.90	$219.90
Purchase #4	$208.25	10.144%	$229.3749	$229.37	$229.35	$229.40
Purchase #5	$215.27	7.517%	$231.4518	$231.45	$231.45	$231.50
Purchase #6	$105.27	10.468%	$116.2897	$116.29	$116.30	$116.30
Purchase #7	$233.43	12.513%	$262.6391	$262.64	$262.65	$262.60
7 purchase totals =	$1,138.20		$1,241.8936	$1,241.89	$1,241.90	$1,241.90