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	$94.64	3.118%	$97.5909	$97.59	$97.60	$97.60
Purchase #2	$196.36	11.571%	$219.0808	$219.08	$219.10	$219.10
Purchase #3	$59.37	12.722%	$66.9231	$66.92	$66.90	$66.90
Purchase #4	$118.98	10.375%	$131.3242	$131.32	$131.30	$131.30
Purchase #5	$50.58	5.661%	$53.4433	$53.44	$53.45	$53.40
Purchase #6	$107.30	3.580%	$111.1413	$111.14	$111.15	$111.10
Purchase #7	$239.55	3.548%	$248.0492	$248.05	$248.05	$248.00
7 purchase totals =	$866.78		$927.5528	$927.54	$927.55	$927.40