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	$132.98	13.136%	$150.4483	$150.45	$150.45	$150.40
Purchase #2	$10.66	6.151%	$11.3157	$11.32	$11.30	$11.30
Purchase #3	$233.41	8.169%	$252.4773	$252.48	$252.50	$252.50
Purchase #4	$11.26	8.188%	$12.182	$12.18	$12.20	$12.20
Purchase #5	$247.31	4.636%	$258.7753	$258.78	$258.80	$258.80
Purchase #6	$218.48	11.111%	$242.7553	$242.76	$242.75	$242.80
Purchase #7	$84.83	4.831%	$88.9281	$88.93	$88.95	$88.90
7 purchase totals =	$938.93		$1,016.8820	$1,016.90	$1,016.95	$1,016.90