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	$95.34	10.192%	$105.0571	$105.06	$105.05	$105.10
Purchase #2	$90.94	12.709%	$102.4976	$102.50	$102.50	$102.50
Purchase #3	$238.43	13.545%	$270.7253	$270.73	$270.75	$270.70
Purchase #4	$127.90	3.231%	$132.0324	$132.03	$132.05	$132.00
Purchase #5	$197.84	6.634%	$210.9647	$210.96	$210.95	$211.00
Purchase #6	$48.82	12.272%	$54.8112	$54.81	$54.80	$54.80
Purchase #7	$126.43	13.640%	$143.6751	$143.68	$143.70	$143.70
7 purchase totals =	$925.70		$1,019.7634	$1,019.77	$1,019.80	$1,019.80