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	$166.38	5.347%	$175.2763	$175.28	$175.30	$175.30
Purchase #2	$99.40	10.128%	$109.4672	$109.47	$109.45	$109.50
Purchase #3	$66.69	9.374%	$72.9415	$72.94	$72.95	$72.90
Purchase #4	$73.37	3.531%	$75.9607	$75.96	$75.95	$76.00
Purchase #5	$50.41	10.497%	$55.7015	$55.70	$55.70	$55.70
Purchase #6	$183.74	7.171%	$196.916	$196.92	$196.90	$196.90
Purchase #7	$102.47	8.666%	$111.3501	$111.35	$111.35	$111.40
7 purchase totals =	$742.46		$797.6133	$797.62	$797.60	$797.70