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	$149.60	10.446%	$165.2272	$165.23	$165.25	$165.20
Purchase #2	$30.57	4.808%	$32.0398	$32.04	$32.05	$32.00
Purchase #3	$36.82	5.587%	$38.8771	$38.88	$38.90	$38.90
Purchase #4	$125.36	10.534%	$138.5654	$138.57	$138.55	$138.60
Purchase #5	$73.85	6.802%	$78.8733	$78.87	$78.85	$78.90
Purchase #6	$37.69	6.553%	$40.1598	$40.16	$40.15	$40.20
Purchase #7	$197.46	4.237%	$205.8264	$205.83	$205.85	$205.80
7 purchase totals =	$651.35		$699.5690	$699.58	$699.60	$699.60