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	$99.69	5.476%	$105.149	$105.15	$105.15	$105.10
Purchase #2	$56.55	4.626%	$59.166	$59.17	$59.15	$59.20
Purchase #3	$247.29	5.743%	$261.4919	$261.49	$261.50	$261.50
Purchase #4	$84.40	6.663%	$90.0236	$90.02	$90.00	$90.00
Purchase #5	$83.60	12.826%	$94.3225	$94.32	$94.30	$94.30
Purchase #6	$57.66	13.374%	$65.3714	$65.37	$65.35	$65.40
Purchase #7	$152.69	12.659%	$172.019	$172.02	$172.00	$172.00
7 purchase totals =	$781.88		$847.5434	$847.54	$847.45	$847.50