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	$180.26	5.656%	$190.4555	$190.46	$190.45	$190.50
Purchase #2	$34.85	8.353%	$37.761	$37.76	$37.75	$37.80
Purchase #3	$173.51	10.172%	$191.1594	$191.16	$191.15	$191.20
Purchase #4	$239.48	3.393%	$247.6056	$247.61	$247.60	$247.60
Purchase #5	$250.55	8.753%	$272.4806	$272.48	$272.50	$272.50
Purchase #6	$72.52	11.779%	$81.0621	$81.06	$81.05	$81.10
Purchase #7	$101.44	7.476%	$109.0237	$109.02	$109.00	$109.00
7 purchase totals =	$1,052.61		$1,129.5479	$1,129.55	$1,129.50	$1,129.70