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	$161.51	12.405%	$181.5453	$181.55	$181.55	$181.50
Purchase #2	$145.73	8.805%	$158.5615	$158.56	$158.55	$158.60
Purchase #3	$120.68	3.819%	$125.2888	$125.29	$125.30	$125.30
Purchase #4	$107.44	4.612%	$112.3951	$112.40	$112.40	$112.40
Purchase #5	$74.65	5.597%	$78.8282	$78.83	$78.85	$78.80
Purchase #6	$39.67	7.341%	$42.5822	$42.58	$42.60	$42.60
Purchase #7	$54.33	12.500%	$61.1213	$61.12	$61.10	$61.10
7 purchase totals =	$704.01		$760.3224	$760.33	$760.35	$760.30