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	$137.46	6.528%	$146.4334	$146.43	$146.45	$146.40
Purchase #2	$105.70	5.406%	$111.4141	$111.41	$111.40	$111.40
Purchase #3	$194.86	7.849%	$210.1546	$210.15	$210.15	$210.20
Purchase #4	$170.87	11.713%	$190.884	$190.88	$190.90	$190.90
Purchase #5	$134.46	5.127%	$141.3538	$141.35	$141.35	$141.40
Purchase #6	$207.60	9.120%	$226.5331	$226.53	$226.55	$226.50
Purchase #7	$86.29	7.569%	$92.8213	$92.82	$92.80	$92.80
7 purchase totals =	$1,037.24		$1,119.5943	$1,119.57	$1,119.60	$1,119.60