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	$180.81	7.773%	$194.8644	$194.86	$194.85	$194.90
Purchase #2	$57.67	8.390%	$62.5085	$62.51	$62.50	$62.50
Purchase #3	$115.30	10.717%	$127.6567	$127.66	$127.65	$127.70
Purchase #4	$218.93	13.258%	$247.9557	$247.96	$247.95	$248.00
Purchase #5	$99.86	9.466%	$109.3127	$109.31	$109.30	$109.30
Purchase #6	$26.38	5.769%	$27.9019	$27.90	$27.90	$27.90
Purchase #7	$106.43	9.813%	$116.874	$116.87	$116.85	$116.90
7 purchase totals =	$805.38		$887.0739	$887.07	$887.00	$887.20