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	$221.61	4.316%	$231.1747	$231.17	$231.15	$231.20
Purchase #2	$195.45	8.379%	$211.8268	$211.83	$211.85	$211.80
Purchase #3	$37.89	11.119%	$42.103	$42.10	$42.10	$42.10
Purchase #4	$81.84	9.295%	$89.447	$89.45	$89.45	$89.40
Purchase #5	$200.54	7.261%	$215.1012	$215.10	$215.10	$215.10
Purchase #6	$247.48	12.453%	$278.2987	$278.30	$278.30	$278.30
Purchase #7	$116.81	10.321%	$128.866	$128.87	$128.85	$128.90
7 purchase totals =	$1,101.62		$1,196.8174	$1,196.82	$1,196.80	$1,196.80