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	$116.31	9.194%	$127.0035	$127.00	$127.00	$127.00
Purchase #2	$59.31	3.579%	$61.4327	$61.43	$61.45	$61.40
Purchase #3	$237.92	6.484%	$253.3467	$253.35	$253.35	$253.30
Purchase #4	$44.61	4.585%	$46.6554	$46.66	$46.65	$46.70
Purchase #5	$16.89	7.639%	$18.1802	$18.18	$18.20	$18.20
Purchase #6	$91.55	9.471%	$100.2207	$100.22	$100.20	$100.20
Purchase #7	$249.74	3.166%	$257.6468	$257.65	$257.65	$257.60
7 purchase totals =	$816.33		$864.4860	$864.49	$864.50	$864.40