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	$10.87	9.271%	$11.8778	$11.88	$11.90	$11.90
Purchase #2	$168.96	3.126%	$174.2417	$174.24	$174.25	$174.20
Purchase #3	$146.43	8.110%	$158.3055	$158.31	$158.30	$158.30
Purchase #4	$41.25	4.779%	$43.2213	$43.22	$43.20	$43.20
Purchase #5	$184.29	3.420%	$190.5927	$190.59	$190.60	$190.60
Purchase #6	$12.50	8.747%	$13.5934	$13.59	$13.60	$13.60
Purchase #7	$98.98	13.265%	$112.1097	$112.11	$112.10	$112.10
7 purchase totals =	$663.28		$703.9421	$703.94	$703.95	$703.90