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	$32.33	10.131%	$35.6054	$35.61	$35.60	$35.60
Purchase #2	$132.41	6.750%	$141.3477	$141.35	$141.35	$141.30
Purchase #3	$45.82	5.573%	$48.3735	$48.37	$48.35	$48.40
Purchase #4	$183.39	3.700%	$190.1754	$190.18	$190.20	$190.20
Purchase #5	$157.44	4.359%	$164.3028	$164.30	$164.30	$164.30
Purchase #6	$222.28	13.750%	$252.8435	$252.84	$252.85	$252.80
Purchase #7	$216.31	12.262%	$242.8339	$242.83	$242.85	$242.80
7 purchase totals =	$989.98		$1,075.4822	$1,075.48	$1,075.50	$1,075.40