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	$30.88	5.795%	$32.6695	$32.67	$32.65	$32.70
Purchase #2	$58.92	12.660%	$66.3793	$66.38	$66.40	$66.40
Purchase #3	$90.31	10.388%	$99.6914	$99.69	$99.70	$99.70
Purchase #4	$185.86	3.151%	$191.7164	$191.72	$191.70	$191.70
Purchase #5	$86.54	5.456%	$91.2616	$91.26	$91.25	$91.30
Purchase #6	$244.98	7.241%	$262.719	$262.72	$262.70	$262.70
Purchase #7	$136.46	10.377%	$150.6205	$150.62	$150.60	$150.60
7 purchase totals =	$833.95		$895.0577	$895.06	$895.00	$895.10