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	$121.39	9.286%	$132.6623	$132.66	$132.65	$132.70
Purchase #2	$99.67	4.765%	$104.4193	$104.42	$104.40	$104.40
Purchase #3	$181.31	7.499%	$194.9064	$194.91	$194.90	$194.90
Purchase #4	$145.64	3.346%	$150.5131	$150.51	$150.50	$150.50
Purchase #5	$147.64	9.715%	$161.9832	$161.98	$162.00	$162.00
Purchase #6	$247.89	7.670%	$266.9032	$266.90	$266.90	$266.90
Purchase #7	$165.92	5.105%	$174.3902	$174.39	$174.40	$174.40
7 purchase totals =	$1,109.46		$1,185.7777	$1,185.77	$1,185.75	$1,185.80