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	$173.54	5.230%	$182.6161	$182.62	$182.60	$182.60
Purchase #2	$12.60	9.505%	$13.7976	$13.80	$13.80	$13.80
Purchase #3	$30.52	4.468%	$31.8836	$31.88	$31.90	$31.90
Purchase #4	$12.72	12.292%	$14.2835	$14.28	$14.30	$14.30
Purchase #5	$130.69	11.650%	$145.9154	$145.92	$145.90	$145.90
Purchase #6	$118.93	3.425%	$123.0034	$123.00	$123.00	$123.00
Purchase #7	$134.95	12.253%	$151.4854	$151.49	$151.50	$151.50
7 purchase totals =	$613.95		$662.9850	$662.99	$663.00	$663.00