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	$146.55	4.129%	$152.601	$152.60	$152.60	$152.60
Purchase #2	$97.81	6.578%	$104.2439	$104.24	$104.25	$104.20
Purchase #3	$46.48	4.615%	$48.6251	$48.63	$48.65	$48.60
Purchase #4	$124.77	5.120%	$131.1582	$131.16	$131.15	$131.20
Purchase #5	$6.36	9.296%	$6.9512	$6.95	$6.95	$7.00
Purchase #6	$51.61	11.256%	$57.4192	$57.42	$57.40	$57.40
Purchase #7	$238.94	6.459%	$254.3731	$254.37	$254.35	$254.40
7 purchase totals =	$712.52		$755.3717	$755.37	$755.35	$755.40