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	$165.50	8.563%	$179.6718	$179.67	$179.65	$179.70
Purchase #2	$230.54	11.425%	$256.8792	$256.88	$256.90	$256.90
Purchase #3	$106.82	8.651%	$116.061	$116.06	$116.05	$116.10
Purchase #4	$40.37	10.122%	$44.4563	$44.46	$44.45	$44.50
Purchase #5	$6.60	13.528%	$7.4928	$7.49	$7.50	$7.50
Purchase #6	$92.52	5.836%	$97.9195	$97.92	$97.90	$97.90
Purchase #7	$186.83	6.143%	$198.307	$198.31	$198.30	$198.30
7 purchase totals =	$829.18		$900.7876	$900.79	$900.75	$900.90