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	$88.88	13.200%	$100.6122	$100.61	$100.60	$100.60
Purchase #2	$5.86	13.719%	$6.6639	$6.66	$6.65	$6.70
Purchase #3	$16.72	13.836%	$19.0334	$19.03	$19.05	$19.00
Purchase #4	$153.45	7.431%	$164.8529	$164.85	$164.85	$164.90
Purchase #5	$223.58	13.820%	$254.4788	$254.48	$254.50	$254.50
Purchase #6	$143.83	8.227%	$155.6629	$155.66	$155.65	$155.70
Purchase #7	$59.37	11.850%	$66.4053	$66.41	$66.40	$66.40
7 purchase totals =	$691.69		$767.7094	$767.70	$767.70	$767.80