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	$233.55	9.158%	$254.9385	$254.94	$254.95	$254.90
Purchase #2	$158.32	3.679%	$164.1446	$164.14	$164.15	$164.10
Purchase #3	$41.68	5.644%	$44.0324	$44.03	$44.05	$44.00
Purchase #4	$97.33	11.308%	$108.3361	$108.34	$108.35	$108.30
Purchase #5	$146.39	8.210%	$158.4086	$158.41	$158.40	$158.40
Purchase #6	$74.31	6.122%	$78.8593	$78.86	$78.85	$78.90
Purchase #7	$139.72	13.682%	$158.8365	$158.84	$158.85	$158.80
7 purchase totals =	$891.30		$967.5560	$967.56	$967.60	$967.40