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	$92.91	11.312%	$103.42	$103.42	$103.40	$103.40
Purchase #2	$132.82	10.380%	$146.6067	$146.61	$146.60	$146.60
Purchase #3	$122.45	3.865%	$127.1827	$127.18	$127.20	$127.20
Purchase #4	$46.74	4.219%	$48.712	$48.71	$48.70	$48.70
Purchase #5	$12.94	9.222%	$14.1333	$14.13	$14.15	$14.10
Purchase #6	$189.60	7.498%	$203.8162	$203.82	$203.80	$203.80
Purchase #7	$37.74	8.678%	$41.0151	$41.02	$41.00	$41.00
7 purchase totals =	$635.20		$684.8860	$684.89	$684.85	$684.80