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	$117.91	7.721%	$127.0138	$127.01	$127.00	$127.00
Purchase #2	$197.51	4.118%	$205.6435	$205.64	$205.65	$205.60
Purchase #3	$77.76	4.790%	$81.4847	$81.48	$81.50	$81.50
Purchase #4	$233.39	8.120%	$252.3413	$252.34	$252.35	$252.30
Purchase #5	$98.91	6.740%	$105.5765	$105.58	$105.60	$105.60
Purchase #6	$185.99	13.794%	$211.6455	$211.65	$211.65	$211.60
Purchase #7	$108.93	3.650%	$112.9059	$112.91	$112.90	$112.90
7 purchase totals =	$1,020.40		$1,096.6112	$1,096.61	$1,096.65	$1,096.50