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	$179.33	6.364%	$190.7426	$190.74	$190.75	$190.70
Purchase #2	$222.96	11.186%	$247.9003	$247.90	$247.90	$247.90
Purchase #3	$99.90	7.435%	$107.3276	$107.33	$107.35	$107.30
Purchase #4	$111.95	4.299%	$116.7627	$116.76	$116.75	$116.80
Purchase #5	$218.55	5.420%	$230.3954	$230.40	$230.40	$230.40
Purchase #6	$99.53	11.630%	$111.1053	$111.11	$111.10	$111.10
Purchase #7	$30.48	6.716%	$32.527	$32.53	$32.55	$32.50
7 purchase totals =	$962.70		$1,036.7609	$1,036.77	$1,036.80	$1,036.70