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	$199.92	11.603%	$223.1167	$223.12	$223.10	$223.10
Purchase #2	$221.88	10.203%	$244.5184	$244.52	$244.50	$244.50
Purchase #3	$216.86	5.792%	$229.4205	$229.42	$229.40	$229.40
Purchase #4	$99.91	9.771%	$109.6722	$109.67	$109.65	$109.70
Purchase #5	$70.90	6.136%	$75.2504	$75.25	$75.25	$75.30
Purchase #6	$92.55	8.693%	$100.5954	$100.60	$100.60	$100.60
Purchase #7	$198.28	3.872%	$205.9574	$205.96	$205.95	$206.00
7 purchase totals =	$1,100.30		$1,188.5310	$1,188.54	$1,188.45	$1,188.60