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	$29.31	11.236%	$32.6033	$32.60	$32.60	$32.60
Purchase #2	$16.98	6.572%	$18.0959	$18.10	$18.10	$18.10
Purchase #3	$176.91	6.368%	$188.1756	$188.18	$188.20	$188.20
Purchase #4	$74.50	11.102%	$82.771	$82.77	$82.75	$82.80
Purchase #5	$20.60	4.694%	$21.567	$21.57	$21.55	$21.60
Purchase #6	$220.92	13.361%	$250.4371	$250.44	$250.45	$250.40
Purchase #7	$69.97	4.863%	$73.3726	$73.37	$73.35	$73.40
7 purchase totals =	$609.19		$667.0225	$667.03	$667.00	$667.10