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	$227.38	13.495%	$258.0649	$258.06	$258.05	$258.10
Purchase #2	$42.55	4.586%	$44.5013	$44.50	$44.50	$44.50
Purchase #3	$128.55	11.613%	$143.4785	$143.48	$143.50	$143.50
Purchase #4	$95.44	4.346%	$99.5878	$99.59	$99.60	$99.60
Purchase #5	$197.78	3.696%	$205.0899	$205.09	$205.10	$205.10
Purchase #6	$58.30	11.847%	$65.2068	$65.21	$65.20	$65.20
Purchase #7	$55.64	7.228%	$59.6617	$59.66	$59.65	$59.70
7 purchase totals =	$805.64		$875.5909	$875.59	$875.60	$875.70