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	$67.93	8.204%	$73.503	$73.50	$73.50	$73.50
Purchase #2	$13.63	6.518%	$14.5184	$14.52	$14.50	$14.50
Purchase #3	$64.54	5.849%	$68.3149	$68.31	$68.30	$68.30
Purchase #4	$86.42	5.201%	$90.9147	$90.91	$90.90	$90.90
Purchase #5	$101.71	9.595%	$111.4691	$111.47	$111.45	$111.50
Purchase #6	$107.47	11.831%	$120.1848	$120.18	$120.20	$120.20
Purchase #7	$46.72	3.521%	$48.365	$48.37	$48.35	$48.40
7 purchase totals =	$488.42		$527.2699	$527.26	$527.20	$527.30