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	$234.99	8.158%	$254.1605	$254.16	$254.15	$254.20
Purchase #2	$68.46	6.505%	$72.9133	$72.91	$72.90	$72.90
Purchase #3	$85.43	12.457%	$96.072	$96.07	$96.05	$96.10
Purchase #4	$140.51	4.424%	$146.7262	$146.73	$146.75	$146.70
Purchase #5	$132.98	7.716%	$143.2407	$143.24	$143.25	$143.20
Purchase #6	$217.39	3.446%	$224.8813	$224.88	$224.90	$224.90
Purchase #7	$151.69	5.215%	$159.6006	$159.60	$159.60	$159.60
7 purchase totals =	$1,031.45		$1,097.5946	$1,097.59	$1,097.60	$1,097.60