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	$223.53	13.868%	$254.5291	$254.53	$254.55	$254.50
Purchase #2	$34.64	8.536%	$37.5969	$37.60	$37.60	$37.60
Purchase #3	$27.41	3.115%	$28.2638	$28.26	$28.25	$28.30
Purchase #4	$114.56	3.391%	$118.4447	$118.44	$118.45	$118.40
Purchase #5	$234.58	11.659%	$261.9297	$261.93	$261.95	$261.90
Purchase #6	$101.34	7.847%	$109.2921	$109.29	$109.30	$109.30
Purchase #7	$139.37	9.290%	$152.3175	$152.32	$152.30	$152.30
7 purchase totals =	$875.43		$962.3738	$962.37	$962.40	$962.30