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	$86.89	10.303%	$95.8423	$95.84	$95.85	$95.80
Purchase #2	$122.35	4.227%	$127.5217	$127.52	$127.50	$127.50
Purchase #3	$221.98	11.855%	$248.2957	$248.30	$248.30	$248.30
Purchase #4	$182.83	5.590%	$193.0502	$193.05	$193.05	$193.10
Purchase #5	$50.63	7.535%	$54.445	$54.45	$54.45	$54.40
Purchase #6	$163.52	5.600%	$172.6771	$172.68	$172.70	$172.70
Purchase #7	$63.40	11.862%	$70.9205	$70.92	$70.90	$70.90
7 purchase totals =	$891.60		$962.7525	$962.76	$962.75	$962.70