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	$168.91	4.565%	$176.6207	$176.62	$176.60	$176.60
Purchase #2	$164.30	12.108%	$184.1934	$184.19	$184.20	$184.20
Purchase #3	$145.44	9.694%	$159.539	$159.54	$159.55	$159.50
Purchase #4	$122.51	4.379%	$127.8747	$127.87	$127.85	$127.90
Purchase #5	$65.45	8.230%	$70.8365	$70.84	$70.85	$70.80
Purchase #6	$83.73	10.410%	$92.4463	$92.45	$92.45	$92.40
Purchase #7	$66.46	7.535%	$71.4678	$71.47	$71.45	$71.50
7 purchase totals =	$816.80		$882.9784	$882.98	$882.95	$882.90