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	$222.34	7.206%	$238.3618	$238.36	$238.35	$238.40
Purchase #2	$123.39	7.694%	$132.8836	$132.88	$132.90	$132.90
Purchase #3	$145.35	13.304%	$164.6874	$164.69	$164.70	$164.70
Purchase #4	$98.38	3.287%	$101.6138	$101.61	$101.60	$101.60
Purchase #5	$90.46	8.536%	$98.1817	$98.18	$98.20	$98.20
Purchase #6	$12.79	3.847%	$13.282	$13.28	$13.30	$13.30
Purchase #7	$111.75	4.249%	$116.4983	$116.50	$116.50	$116.50
7 purchase totals =	$804.46		$865.5086	$865.50	$865.55	$865.60