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	$112.70	13.359%	$127.7556	$127.76	$127.75	$127.80
Purchase #2	$154.87	10.654%	$171.3698	$171.37	$171.35	$171.40
Purchase #3	$133.40	3.366%	$137.8902	$137.89	$137.90	$137.90
Purchase #4	$46.29	3.587%	$47.9504	$47.95	$47.95	$48.00
Purchase #5	$91.42	9.267%	$99.8919	$99.89	$99.90	$99.90
Purchase #6	$168.37	6.673%	$179.6053	$179.61	$179.60	$179.60
Purchase #7	$9.34	7.607%	$10.0505	$10.05	$10.05	$10.10
7 purchase totals =	$716.39		$774.5137	$774.52	$774.50	$774.70