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	$49.65	7.586%	$53.4164	$53.42	$53.40	$53.40
Purchase #2	$50.72	3.471%	$52.4805	$52.48	$52.50	$52.50
Purchase #3	$128.87	6.404%	$137.1228	$137.12	$137.10	$137.10
Purchase #4	$177.29	4.479%	$185.2308	$185.23	$185.25	$185.20
Purchase #5	$62.28	10.375%	$68.7416	$68.74	$68.75	$68.70
Purchase #6	$174.82	12.413%	$196.5204	$196.52	$196.50	$196.50
Purchase #7	$10.60	5.862%	$11.2214	$11.22	$11.20	$11.20
7 purchase totals =	$654.23		$704.7339	$704.73	$704.70	$704.60