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	$195.51	4.574%	$204.4526	$204.45	$204.45	$204.50
Purchase #2	$34.88	4.194%	$36.3429	$36.34	$36.35	$36.30
Purchase #3	$99.33	12.842%	$112.086	$112.09	$112.10	$112.10
Purchase #4	$47.94	3.472%	$49.6045	$49.60	$49.60	$49.60
Purchase #5	$81.46	11.147%	$90.5403	$90.54	$90.55	$90.50
Purchase #6	$160.52	8.806%	$174.6554	$174.66	$174.65	$174.70
Purchase #7	$156.92	3.371%	$162.2098	$162.21	$162.20	$162.20
7 purchase totals =	$776.56		$829.8915	$829.89	$829.90	$829.90