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	$13.95	13.198%	$15.7911	$15.79	$15.80	$15.80
Purchase #2	$95.94	5.593%	$101.3059	$101.31	$101.30	$101.30
Purchase #3	$207.44	13.248%	$234.9217	$234.92	$234.90	$234.90
Purchase #4	$54.88	6.754%	$58.5866	$58.59	$58.60	$58.60
Purchase #5	$215.92	8.198%	$233.6211	$233.62	$233.60	$233.60
Purchase #6	$52.44	3.172%	$54.1034	$54.10	$54.10	$54.10
Purchase #7	$99.86	11.498%	$111.3419	$111.34	$111.35	$111.30
7 purchase totals =	$740.43		$809.6717	$809.67	$809.65	$809.60