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	$101.83	7.553%	$109.5212	$109.52	$109.50	$109.50
Purchase #2	$237.71	13.311%	$269.3516	$269.35	$269.35	$269.40
Purchase #3	$184.44	7.261%	$197.8322	$197.83	$197.85	$197.80
Purchase #4	$135.71	7.625%	$146.0579	$146.06	$146.05	$146.10
Purchase #5	$118.92	7.345%	$127.6547	$127.65	$127.65	$127.70
Purchase #6	$108.29	13.579%	$122.9947	$122.99	$123.00	$123.00
Purchase #7	$89.66	9.380%	$98.0701	$98.07	$98.05	$98.10
7 purchase totals =	$976.56		$1,071.4824	$1,071.47	$1,071.45	$1,071.60