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	$105.66	8.477%	$114.6168	$114.62	$114.60	$114.60
Purchase #2	$196.52	7.328%	$210.921	$210.92	$210.90	$210.90
Purchase #3	$130.81	11.242%	$145.5157	$145.52	$145.50	$145.50
Purchase #4	$145.41	3.128%	$149.9584	$149.96	$149.95	$150.00
Purchase #5	$178.37	10.754%	$197.5519	$197.55	$197.55	$197.60
Purchase #6	$53.50	4.572%	$55.946	$55.95	$55.95	$55.90
Purchase #7	$244.61	12.761%	$275.8247	$275.82	$275.80	$275.80
7 purchase totals =	$1,054.88		$1,150.3345	$1,150.34	$1,150.25	$1,150.30