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	$90.43	13.261%	$102.4219	$102.42	$102.40	$102.40
Purchase #2	$6.68	13.464%	$7.5794	$7.58	$7.60	$7.60
Purchase #3	$109.42	8.133%	$118.3191	$118.32	$118.30	$118.30
Purchase #4	$19.64	9.505%	$21.5068	$21.51	$21.50	$21.50
Purchase #5	$131.51	11.213%	$146.2562	$146.26	$146.25	$146.30
Purchase #6	$112.46	13.744%	$127.9165	$127.92	$127.90	$127.90
Purchase #7	$163.44	5.743%	$172.8264	$172.83	$172.85	$172.80
7 purchase totals =	$633.58		$696.8263	$696.84	$696.80	$696.80