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	$91.97	10.452%	$101.5827	$101.58	$101.60	$101.60
Purchase #2	$92.25	7.612%	$99.2721	$99.27	$99.25	$99.30
Purchase #3	$47.30	6.809%	$50.5207	$50.52	$50.50	$50.50
Purchase #4	$20.32	5.622%	$21.4624	$21.46	$21.45	$21.50
Purchase #5	$230.93	9.784%	$253.5242	$253.52	$253.50	$253.50
Purchase #6	$219.95	13.106%	$248.7766	$248.78	$248.80	$248.80
Purchase #7	$13.79	7.110%	$14.7705	$14.77	$14.75	$14.80
7 purchase totals =	$716.51		$789.9092	$789.90	$789.85	$790.00