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	$175.94	13.865%	$200.3341	$200.33	$200.35	$200.30
Purchase #2	$96.35	9.128%	$105.1448	$105.14	$105.15	$105.10
Purchase #3	$191.45	4.540%	$200.1418	$200.14	$200.15	$200.10
Purchase #4	$174.59	5.554%	$184.2867	$184.29	$184.30	$184.30
Purchase #5	$154.66	8.699%	$168.1139	$168.11	$168.10	$168.10
Purchase #6	$209.70	10.527%	$231.7751	$231.78	$231.80	$231.80
Purchase #7	$249.99	11.816%	$279.5288	$279.53	$279.55	$279.50
7 purchase totals =	$1,252.68		$1,369.3252	$1,369.32	$1,369.40	$1,369.20