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	$210.75	9.578%	$230.9356	$230.94	$230.95	$230.90
Purchase #2	$137.59	3.180%	$141.9654	$141.97	$141.95	$142.00
Purchase #3	$48.42	4.425%	$50.5626	$50.56	$50.55	$50.60
Purchase #4	$25.31	8.480%	$27.4563	$27.46	$27.45	$27.50
Purchase #5	$126.72	4.390%	$132.283	$132.28	$132.30	$132.30
Purchase #6	$76.29	11.386%	$84.9764	$84.98	$85.00	$85.00
Purchase #7	$33.92	10.272%	$37.4043	$37.40	$37.40	$37.40
7 purchase totals =	$659.00		$705.5836	$705.59	$705.60	$705.70