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	$14.56	7.772%	$15.6916	$15.69	$15.70	$15.70
Purchase #2	$55.99	10.420%	$61.8242	$61.82	$61.80	$61.80
Purchase #3	$57.35	5.357%	$60.4222	$60.42	$60.40	$60.40
Purchase #4	$70.71	8.166%	$76.4842	$76.48	$76.50	$76.50
Purchase #5	$248.69	11.244%	$276.6527	$276.65	$276.65	$276.70
Purchase #6	$134.85	6.432%	$143.5236	$143.52	$143.50	$143.50
Purchase #7	$36.30	4.400%	$37.8972	$37.90	$37.90	$37.90
7 purchase totals =	$618.45		$672.4957	$672.48	$672.45	$672.50