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	$201.84	12.806%	$227.6876	$227.69	$227.70	$227.70
Purchase #2	$122.43	12.517%	$137.7546	$137.75	$137.75	$137.80
Purchase #3	$144.66	4.594%	$151.3057	$151.31	$151.30	$151.30
Purchase #4	$229.53	10.720%	$254.1356	$254.14	$254.15	$254.10
Purchase #5	$155.62	12.228%	$174.6492	$174.65	$174.65	$174.60
Purchase #6	$246.43	10.322%	$271.8665	$271.87	$271.85	$271.90
Purchase #7	$123.59	3.282%	$127.6462	$127.65	$127.65	$127.60
7 purchase totals =	$1,224.10		$1,345.0454	$1,345.06	$1,345.05	$1,345.00