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	$112.98	12.554%	$127.1635	$127.16	$127.15	$127.20
Purchase #2	$30.99	11.598%	$34.5842	$34.58	$34.60	$34.60
Purchase #3	$100.29	5.412%	$105.7177	$105.72	$105.70	$105.70
Purchase #4	$80.96	8.218%	$87.6133	$87.61	$87.60	$87.60
Purchase #5	$180.99	11.120%	$201.1161	$201.12	$201.10	$201.10
Purchase #6	$144.85	12.191%	$162.5087	$162.51	$162.50	$162.50
Purchase #7	$86.39	3.504%	$89.4171	$89.42	$89.40	$89.40
7 purchase totals =	$737.45		$808.1206	$808.12	$808.05	$808.10