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	$118.28	11.726%	$132.1495	$132.15	$132.15	$132.10
Purchase #2	$21.33	7.819%	$22.9978	$23.00	$23.00	$23.00
Purchase #3	$47.60	12.277%	$53.4439	$53.44	$53.45	$53.40
Purchase #4	$43.41	7.481%	$46.6575	$46.66	$46.65	$46.70
Purchase #5	$91.42	10.265%	$100.8043	$100.80	$100.80	$100.80
Purchase #6	$79.66	8.581%	$86.4956	$86.50	$86.50	$86.50
Purchase #7	$33.47	10.569%	$37.0074	$37.01	$37.00	$37.00
7 purchase totals =	$435.17		$479.5560	$479.56	$479.55	$479.50