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	$201.25	7.196%	$215.732	$215.73	$215.75	$215.70
Purchase #2	$242.82	3.866%	$252.2074	$252.21	$252.20	$252.20
Purchase #3	$12.38	4.713%	$12.9635	$12.96	$12.95	$13.00
Purchase #4	$99.67	12.212%	$111.8417	$111.84	$111.85	$111.80
Purchase #5	$76.79	8.203%	$83.0891	$83.09	$83.10	$83.10
Purchase #6	$105.27	4.386%	$109.8871	$109.89	$109.90	$109.90
Purchase #7	$211.72	10.556%	$234.0692	$234.07	$234.05	$234.10
7 purchase totals =	$949.90		$1,019.7900	$1,019.79	$1,019.80	$1,019.80