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	$240.54	13.466%	$272.9311	$272.93	$272.95	$272.90
Purchase #2	$227.53	3.396%	$235.2569	$235.26	$235.25	$235.30
Purchase #3	$229.43	11.505%	$255.8259	$255.83	$255.85	$255.80
Purchase #4	$160.85	5.276%	$169.3364	$169.34	$169.35	$169.30
Purchase #5	$177.83	10.379%	$196.287	$196.29	$196.30	$196.30
Purchase #6	$152.48	6.602%	$162.5467	$162.55	$162.55	$162.50
Purchase #7	$180.97	12.844%	$204.2138	$204.21	$204.20	$204.20
7 purchase totals =	$1,369.63		$1,496.3978	$1,496.41	$1,496.45	$1,496.30