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	$172.60	10.733%	$191.1252	$191.13	$191.15	$191.10
Purchase #2	$234.81	9.572%	$257.286	$257.29	$257.30	$257.30
Purchase #3	$151.61	5.688%	$160.2336	$160.23	$160.25	$160.20
Purchase #4	$135.31	12.342%	$152.01	$152.01	$152.00	$152.00
Purchase #5	$70.58	8.394%	$76.5045	$76.50	$76.50	$76.50
Purchase #6	$166.78	8.834%	$181.5133	$181.51	$181.50	$181.50
Purchase #7	$86.63	3.737%	$89.8674	$89.87	$89.85	$89.90
7 purchase totals =	$1,018.32		$1,108.5400	$1,108.54	$1,108.55	$1,108.50