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	$172.43	10.803%	$191.0576	$191.06	$191.05	$191.10
Purchase #2	$199.39	6.394%	$212.139	$212.14	$212.15	$212.10
Purchase #3	$166.58	4.721%	$174.4442	$174.44	$174.45	$174.40
Purchase #4	$137.50	10.461%	$151.8839	$151.88	$151.90	$151.90
Purchase #5	$121.45	5.327%	$127.9196	$127.92	$127.90	$127.90
Purchase #6	$123.75	13.723%	$140.7322	$140.73	$140.75	$140.70
Purchase #7	$7.66	11.744%	$8.5596	$8.56	$8.55	$8.60
7 purchase totals =	$928.76		$1,006.7361	$1,006.73	$1,006.75	$1,006.70