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	$9.71	4.832%	$10.1792	$10.18	$10.20	$10.20
Purchase #2	$231.96	10.625%	$256.6058	$256.61	$256.60	$256.60
Purchase #3	$65.68	7.456%	$70.5771	$70.58	$70.60	$70.60
Purchase #4	$88.60	11.187%	$98.5117	$98.51	$98.50	$98.50
Purchase #5	$89.89	4.108%	$93.5827	$93.58	$93.60	$93.60
Purchase #6	$46.62	13.162%	$52.7561	$52.76	$52.75	$52.80
Purchase #7	$141.95	4.462%	$148.2838	$148.28	$148.30	$148.30
7 purchase totals =	$674.41		$730.4964	$730.50	$730.55	$730.60