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	$48.84	3.823%	$50.7072	$50.71	$50.70	$50.70
Purchase #2	$142.59	7.829%	$153.7534	$153.75	$153.75	$153.80
Purchase #3	$174.61	13.325%	$197.8768	$197.88	$197.90	$197.90
Purchase #4	$194.39	4.698%	$203.5224	$203.52	$203.50	$203.50
Purchase #5	$196.30	13.667%	$223.1283	$223.13	$223.15	$223.10
Purchase #6	$154.86	9.686%	$169.8597	$169.86	$169.85	$169.90
Purchase #7	$17.27	7.771%	$18.6121	$18.61	$18.60	$18.60
7 purchase totals =	$928.86		$1,017.4599	$1,017.46	$1,017.45	$1,017.50