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	$143.81	11.136%	$159.8247	$159.82	$159.80	$159.80
Purchase #2	$178.25	9.730%	$195.5937	$195.59	$195.60	$195.60
Purchase #3	$187.30	4.297%	$195.3483	$195.35	$195.35	$195.30
Purchase #4	$105.42	5.494%	$111.2118	$111.21	$111.20	$111.20
Purchase #5	$57.50	5.356%	$60.5797	$60.58	$60.60	$60.60
Purchase #6	$138.40	5.409%	$145.8861	$145.89	$145.90	$145.90
Purchase #7	$118.89	6.339%	$126.4264	$126.43	$126.45	$126.40
7 purchase totals =	$929.57		$994.8707	$994.87	$994.90	$994.80