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	$173.65	7.586%	$186.8231	$186.82	$186.80	$186.80
Purchase #2	$81.26	13.241%	$92.0196	$92.02	$92.00	$92.00
Purchase #3	$243.55	4.771%	$255.1698	$255.17	$255.15	$255.20
Purchase #4	$37.41	5.862%	$39.603	$39.60	$39.60	$39.60
Purchase #5	$87.28	13.794%	$99.3194	$99.32	$99.30	$99.30
Purchase #6	$37.26	11.672%	$41.609	$41.61	$41.60	$41.60
Purchase #7	$37.86	11.850%	$42.3464	$42.35	$42.35	$42.30
7 purchase totals =	$698.27		$756.8903	$756.89	$756.80	$756.80