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	$88.59	12.257%	$99.4485	$99.45	$99.45	$99.40
Purchase #2	$32.72	7.365%	$35.1298	$35.13	$35.15	$35.10
Purchase #3	$17.67	11.559%	$19.7125	$19.71	$19.70	$19.70
Purchase #4	$38.96	6.563%	$41.5169	$41.52	$41.50	$41.50
Purchase #5	$29.95	11.218%	$33.3098	$33.31	$33.30	$33.30
Purchase #6	$43.68	4.793%	$45.7736	$45.77	$45.75	$45.80
Purchase #7	$192.34	13.551%	$218.404	$218.40	$218.40	$218.40
7 purchase totals =	$443.91		$493.2951	$493.29	$493.25	$493.20