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	$100.51	4.766%	$105.3003	$105.30	$105.30	$105.30
Purchase #2	$177.95	6.811%	$190.0702	$190.07	$190.05	$190.10
Purchase #3	$66.86	11.479%	$74.5349	$74.53	$74.55	$74.50
Purchase #4	$143.81	3.146%	$148.3343	$148.33	$148.35	$148.30
Purchase #5	$150.35	5.543%	$158.6839	$158.68	$158.70	$158.70
Purchase #6	$194.73	4.445%	$203.3857	$203.39	$203.40	$203.40
Purchase #7	$18.25	12.127%	$20.4632	$20.46	$20.45	$20.50
7 purchase totals =	$852.46		$900.7725	$900.76	$900.80	$900.80