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	$199.77	8.483%	$216.7165	$216.72	$216.70	$216.70
Purchase #2	$250.86	9.836%	$275.5346	$275.53	$275.55	$275.50
Purchase #3	$70.77	5.322%	$74.5364	$74.54	$74.55	$74.50
Purchase #4	$153.81	10.778%	$170.3876	$170.39	$170.40	$170.40
Purchase #5	$154.50	11.452%	$172.1933	$172.19	$172.20	$172.20
Purchase #6	$113.37	11.196%	$126.0629	$126.06	$126.05	$126.10
Purchase #7	$99.31	12.589%	$111.8121	$111.81	$111.80	$111.80
7 purchase totals =	$1,042.39		$1,147.2434	$1,147.24	$1,147.25	$1,147.20