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	$160.66	4.334%	$167.623	$167.62	$167.60	$167.60
Purchase #2	$88.63	13.488%	$100.5844	$100.58	$100.60	$100.60
Purchase #3	$130.52	13.464%	$148.0932	$148.09	$148.10	$148.10
Purchase #4	$125.36	9.186%	$136.8756	$136.88	$136.90	$136.90
Purchase #5	$75.57	8.866%	$82.27	$82.27	$82.25	$82.30
Purchase #6	$215.87	6.342%	$229.5605	$229.56	$229.55	$229.60
Purchase #7	$44.58	12.689%	$50.2368	$50.24	$50.25	$50.20
7 purchase totals =	$841.19		$915.2435	$915.24	$915.25	$915.30