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	$148.73	13.423%	$168.694	$168.69	$168.70	$168.70
Purchase #2	$31.92	11.490%	$35.5876	$35.59	$35.60	$35.60
Purchase #3	$96.47	10.733%	$106.8241	$106.82	$106.80	$106.80
Purchase #4	$6.57	7.211%	$7.0438	$7.04	$7.05	$7.00
Purchase #5	$40.64	6.516%	$43.2881	$43.29	$43.30	$43.30
Purchase #6	$50.92	13.450%	$57.7687	$57.77	$57.75	$57.80
Purchase #7	$171.99	10.653%	$190.3121	$190.31	$190.30	$190.30
7 purchase totals =	$547.24		$609.5184	$609.51	$609.50	$609.50