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	$145.46	4.585%	$152.1293	$152.13	$152.15	$152.10
Purchase #2	$152.29	13.410%	$172.7121	$172.71	$172.70	$172.70
Purchase #3	$100.72	6.751%	$107.5196	$107.52	$107.50	$107.50
Purchase #4	$143.60	10.468%	$158.632	$158.63	$158.65	$158.60
Purchase #5	$161.80	10.434%	$178.6822	$178.68	$178.70	$178.70
Purchase #6	$69.82	3.479%	$72.249	$72.25	$72.25	$72.20
Purchase #7	$171.47	8.412%	$185.8941	$185.89	$185.90	$185.90
7 purchase totals =	$945.16		$1,027.8183	$1,027.81	$1,027.85	$1,027.70