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	$86.65	4.562%	$90.603	$90.60	$90.60	$90.60
Purchase #2	$101.74	7.176%	$109.0409	$109.04	$109.05	$109.00
Purchase #3	$59.46	8.646%	$64.6009	$64.60	$64.60	$64.60
Purchase #4	$128.42	10.138%	$141.4392	$141.44	$141.45	$141.40
Purchase #5	$34.80	5.840%	$36.8323	$36.83	$36.85	$36.80
Purchase #6	$160.83	7.264%	$172.5127	$172.51	$172.50	$172.50
Purchase #7	$183.97	11.592%	$205.2958	$205.30	$205.30	$205.30
7 purchase totals =	$755.87		$820.3248	$820.32	$820.35	$820.20