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	$96.72	12.417%	$108.7297	$108.73	$108.75	$108.70
Purchase #2	$95.94	9.719%	$105.2644	$105.26	$105.25	$105.30
Purchase #3	$19.65	9.181%	$21.4541	$21.45	$21.45	$21.50
Purchase #4	$185.43	6.539%	$197.5553	$197.56	$197.55	$197.60
Purchase #5	$28.76	11.757%	$32.1413	$32.14	$32.15	$32.10
Purchase #6	$163.61	6.719%	$174.603	$174.60	$174.60	$174.60
Purchase #7	$247.27	4.549%	$258.5183	$258.52	$258.50	$258.50
7 purchase totals =	$837.38		$898.2661	$898.26	$898.25	$898.30