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	$76.86	7.586%	$82.6906	$82.69	$82.70	$82.70
Purchase #2	$92.38	7.827%	$99.6106	$99.61	$99.60	$99.60
Purchase #3	$103.27	8.383%	$111.9271	$111.93	$111.95	$111.90
Purchase #4	$108.48	7.651%	$116.7798	$116.78	$116.80	$116.80
Purchase #5	$244.77	3.163%	$252.5121	$252.51	$252.50	$252.50
Purchase #6	$178.83	5.262%	$188.24	$188.24	$188.25	$188.20
Purchase #7	$117.76	13.592%	$133.7659	$133.77	$133.75	$133.80
7 purchase totals =	$922.35		$985.5261	$985.53	$985.55	$985.50