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	$181.26	4.493%	$189.404	$189.40	$189.40	$189.40
Purchase #2	$192.50	5.168%	$202.4484	$202.45	$202.45	$202.40
Purchase #3	$56.52	11.152%	$62.8231	$62.82	$62.80	$62.80
Purchase #4	$158.81	6.227%	$168.6991	$168.70	$168.70	$168.70
Purchase #5	$131.95	11.344%	$146.9184	$146.92	$146.90	$146.90
Purchase #6	$122.28	7.184%	$131.0646	$131.06	$131.05	$131.10
Purchase #7	$152.50	4.644%	$159.5821	$159.58	$159.60	$159.60
7 purchase totals =	$995.82		$1,060.9397	$1,060.93	$1,060.90	$1,060.90