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	$33.87	7.435%	$36.3882	$36.39	$36.40	$36.40
Purchase #2	$190.41	7.269%	$204.2509	$204.25	$204.25	$204.30
Purchase #3	$152.52	3.651%	$158.0885	$158.09	$158.10	$158.10
Purchase #4	$76.45	7.284%	$82.0186	$82.02	$82.00	$82.00
Purchase #5	$42.38	9.573%	$46.437	$46.44	$46.45	$46.40
Purchase #6	$95.68	3.610%	$99.134	$99.13	$99.15	$99.10
Purchase #7	$247.25	7.434%	$265.6306	$265.63	$265.65	$265.60
7 purchase totals =	$838.56		$891.9478	$891.95	$892.00	$891.90