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	$212.97	7.468%	$228.8746	$228.87	$228.85	$228.90
Purchase #2	$85.78	5.621%	$90.6017	$90.60	$90.60	$90.60
Purchase #3	$241.30	12.460%	$271.366	$271.37	$271.35	$271.40
Purchase #4	$20.92	4.408%	$21.8422	$21.84	$21.85	$21.80
Purchase #5	$54.32	10.422%	$59.9812	$59.98	$60.00	$60.00
Purchase #6	$94.31	9.350%	$103.128	$103.13	$103.15	$103.10
Purchase #7	$36.81	6.846%	$39.33	$39.33	$39.35	$39.30
7 purchase totals =	$746.41		$815.1237	$815.12	$815.15	$815.10