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	$103.56	11.728%	$115.7055	$115.71	$115.70	$115.70
Purchase #2	$104.30	6.509%	$111.0889	$111.09	$111.10	$111.10
Purchase #3	$89.81	6.453%	$95.6054	$95.61	$95.60	$95.60
Purchase #4	$68.63	12.238%	$77.0289	$77.03	$77.05	$77.00
Purchase #5	$117.90	12.123%	$132.193	$132.19	$132.20	$132.20
Purchase #6	$151.64	5.461%	$159.9211	$159.92	$159.90	$159.90
Purchase #7	$31.50	7.750%	$33.9413	$33.94	$33.95	$33.90
7 purchase totals =	$667.34		$725.4841	$725.49	$725.50	$725.40