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	$192.98	5.463%	$203.5225	$203.52	$203.50	$203.50
Purchase #2	$172.71	10.519%	$190.8774	$190.88	$190.90	$190.90
Purchase #3	$96.27	3.286%	$99.4334	$99.43	$99.45	$99.40
Purchase #4	$194.72	8.397%	$211.0706	$211.07	$211.05	$211.10
Purchase #5	$106.43	4.413%	$111.1268	$111.13	$111.15	$111.10
Purchase #6	$215.77	5.541%	$227.7258	$227.73	$227.75	$227.70
Purchase #7	$147.88	13.673%	$168.0996	$168.10	$168.10	$168.10
7 purchase totals =	$1,126.76		$1,211.8561	$1,211.86	$1,211.90	$1,211.80