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	$120.77	7.724%	$130.0983	$130.10	$130.10	$130.10
Purchase #2	$117.69	11.674%	$131.4291	$131.43	$131.45	$131.40
Purchase #3	$198.70	4.785%	$208.2078	$208.21	$208.20	$208.20
Purchase #4	$56.68	5.332%	$59.7022	$59.70	$59.70	$59.70
Purchase #5	$37.92	10.302%	$41.8265	$41.83	$41.85	$41.80
Purchase #6	$92.54	4.378%	$96.5914	$96.59	$96.60	$96.60
Purchase #7	$58.54	6.171%	$62.1525	$62.15	$62.15	$62.20
7 purchase totals =	$682.84		$730.0078	$730.01	$730.05	$730.00