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	$56.83	13.396%	$64.4429	$64.44	$64.45	$64.40
Purchase #2	$231.88	5.342%	$244.267	$244.27	$244.25	$244.30
Purchase #3	$40.77	3.161%	$42.0587	$42.06	$42.05	$42.10
Purchase #4	$104.61	6.532%	$111.4431	$111.44	$111.45	$111.40
Purchase #5	$10.61	11.757%	$11.8574	$11.86	$11.85	$11.90
Purchase #6	$112.39	6.758%	$119.9853	$119.99	$120.00	$120.00
Purchase #7	$129.74	8.745%	$141.0858	$141.09	$141.10	$141.10
7 purchase totals =	$686.83		$735.1402	$735.15	$735.15	$735.20