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	$37.60	10.151%	$41.4168	$41.42	$41.40	$41.40
Purchase #2	$138.60	6.152%	$147.1267	$147.13	$147.15	$147.10
Purchase #3	$77.46	3.485%	$80.1595	$80.16	$80.15	$80.20
Purchase #4	$82.35	8.388%	$89.2575	$89.26	$89.25	$89.30
Purchase #5	$72.68	11.794%	$81.2519	$81.25	$81.25	$81.30
Purchase #6	$105.89	4.394%	$110.5428	$110.54	$110.55	$110.50
Purchase #7	$246.28	3.864%	$255.7963	$255.80	$255.80	$255.80
7 purchase totals =	$760.86		$805.5515	$805.56	$805.55	$805.60