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	$109.62	7.114%	$117.4184	$117.42	$117.40	$117.40
Purchase #2	$211.64	7.839%	$228.2305	$228.23	$228.25	$228.20
Purchase #3	$173.56	10.556%	$191.881	$191.88	$191.90	$191.90
Purchase #4	$105.26	10.771%	$116.5976	$116.60	$116.60	$116.60
Purchase #5	$60.50	8.205%	$65.464	$65.46	$65.45	$65.50
Purchase #6	$24.79	11.268%	$27.5833	$27.58	$27.60	$27.60
Purchase #7	$107.27	8.512%	$116.4008	$116.40	$116.40	$116.40
7 purchase totals =	$792.64		$863.5756	$863.57	$863.60	$863.60