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	$117.77	8.364%	$127.6203	$127.62	$127.60	$127.60
Purchase #2	$23.64	11.220%	$26.2924	$26.29	$26.30	$26.30
Purchase #3	$99.67	12.334%	$111.9633	$111.96	$111.95	$112.00
Purchase #4	$219.59	10.680%	$243.0422	$243.04	$243.05	$243.00
Purchase #5	$102.94	4.485%	$107.5569	$107.56	$107.55	$107.60
Purchase #6	$108.70	3.668%	$112.6871	$112.69	$112.70	$112.70
Purchase #7	$41.83	8.800%	$45.511	$45.51	$45.50	$45.50
7 purchase totals =	$714.14		$774.6732	$774.67	$774.65	$774.70