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	$200.53	9.272%	$219.1231	$219.12	$219.10	$219.10
Purchase #2	$38.85	11.196%	$43.1996	$43.20	$43.20	$43.20
Purchase #3	$132.45	10.385%	$146.2049	$146.20	$146.20	$146.20
Purchase #4	$215.82	9.739%	$236.8387	$236.84	$236.85	$236.80
Purchase #5	$54.52	8.728%	$59.2785	$59.28	$59.30	$59.30
Purchase #6	$35.73	4.385%	$37.2968	$37.30	$37.30	$37.30
Purchase #7	$118.59	4.624%	$124.0736	$124.07	$124.05	$124.10
7 purchase totals =	$796.49		$866.0152	$866.01	$866.00	$866.00