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	$43.81	4.262%	$45.6772	$45.68	$45.70	$45.70
Purchase #2	$184.51	10.675%	$204.2064	$204.21	$204.20	$204.20
Purchase #3	$210.47	5.728%	$222.5257	$222.53	$222.55	$222.50
Purchase #4	$147.37	10.161%	$162.3443	$162.34	$162.35	$162.30
Purchase #5	$36.32	3.243%	$37.4979	$37.50	$37.50	$37.50
Purchase #6	$214.72	3.398%	$222.0162	$222.02	$222.00	$222.00
Purchase #7	$241.90	5.499%	$255.2021	$255.20	$255.20	$255.20
7 purchase totals =	$1,079.10		$1,149.4698	$1,149.48	$1,149.50	$1,149.40