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	$184.39	4.637%	$192.9402	$192.94	$192.95	$192.90
Purchase #2	$135.46	12.381%	$152.2313	$152.23	$152.25	$152.20
Purchase #3	$91.67	11.392%	$102.113	$102.11	$102.10	$102.10
Purchase #4	$242.91	3.777%	$252.0847	$252.08	$252.10	$252.10
Purchase #5	$214.38	3.372%	$221.6089	$221.61	$221.60	$221.60
Purchase #6	$90.92	10.593%	$100.5512	$100.55	$100.55	$100.60
Purchase #7	$96.98	9.420%	$106.1155	$106.12	$106.10	$106.10
7 purchase totals =	$1,056.71		$1,127.6448	$1,127.64	$1,127.65	$1,127.60