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	$151.82	11.189%	$168.8071	$168.81	$168.80	$168.80
Purchase #2	$163.56	12.730%	$184.3812	$184.38	$184.40	$184.40
Purchase #3	$108.61	7.309%	$116.5483	$116.55	$116.55	$116.50
Purchase #4	$136.41	13.251%	$154.4857	$154.49	$154.50	$154.50
Purchase #5	$68.28	8.719%	$74.2333	$74.23	$74.25	$74.20
Purchase #6	$170.27	11.775%	$190.3193	$190.32	$190.30	$190.30
Purchase #7	$118.56	10.374%	$130.8594	$130.86	$130.85	$130.90
7 purchase totals =	$917.51		$1,019.6343	$1,019.64	$1,019.65	$1,019.60