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	$107.67	8.133%	$116.4268	$116.43	$116.45	$116.40
Purchase #2	$191.62	12.353%	$215.2908	$215.29	$215.30	$215.30
Purchase #3	$159.51	7.291%	$171.1399	$171.14	$171.15	$171.10
Purchase #4	$99.46	5.712%	$105.1412	$105.14	$105.15	$105.10
Purchase #5	$85.36	6.307%	$90.7437	$90.74	$90.75	$90.70
Purchase #6	$164.52	6.137%	$174.6166	$174.62	$174.60	$174.60
Purchase #7	$54.89	11.374%	$61.1332	$61.13	$61.15	$61.10
7 purchase totals =	$863.03		$934.4922	$934.49	$934.55	$934.30