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	$127.86	10.318%	$141.0526	$141.05	$141.05	$141.10
Purchase #2	$132.80	11.695%	$148.331	$148.33	$148.35	$148.30
Purchase #3	$209.61	10.540%	$231.7029	$231.70	$231.70	$231.70
Purchase #4	$95.75	4.505%	$100.0635	$100.06	$100.05	$100.10
Purchase #5	$66.60	6.842%	$71.1568	$71.16	$71.15	$71.20
Purchase #6	$42.28	12.443%	$47.5409	$47.54	$47.55	$47.50
Purchase #7	$167.50	3.543%	$173.4345	$173.43	$173.45	$173.40
7 purchase totals =	$842.40		$913.2822	$913.27	$913.30	$913.30