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	$104.84	6.123%	$111.2594	$111.26	$111.25	$111.30
Purchase #2	$162.58	5.709%	$171.8617	$171.86	$171.85	$171.90
Purchase #3	$213.51	13.379%	$242.0755	$242.08	$242.10	$242.10
Purchase #4	$40.45	6.168%	$42.945	$42.95	$42.95	$42.90
Purchase #5	$100.77	4.694%	$105.5001	$105.50	$105.50	$105.50
Purchase #6	$14.86	8.797%	$16.1672	$16.17	$16.15	$16.20
Purchase #7	$14.91	3.243%	$15.3935	$15.39	$15.40	$15.40
7 purchase totals =	$651.92		$705.2024	$705.21	$705.20	$705.30