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	$238.31	8.547%	$258.6784	$258.68	$258.70	$258.70
Purchase #2	$190.43	3.132%	$196.3943	$196.39	$196.40	$196.40
Purchase #3	$18.47	8.146%	$19.9746	$19.97	$19.95	$20.00
Purchase #4	$105.97	3.332%	$109.5009	$109.50	$109.50	$109.50
Purchase #5	$117.72	13.488%	$133.5981	$133.60	$133.60	$133.60
Purchase #6	$204.31	3.159%	$210.7642	$210.76	$210.75	$210.80
Purchase #7	$104.45	11.338%	$116.2925	$116.29	$116.30	$116.30
7 purchase totals =	$979.66		$1,045.2030	$1,045.19	$1,045.20	$1,045.30