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	$85.69	4.864%	$89.858	$89.86	$89.85	$89.90
Purchase #2	$79.31	8.370%	$85.9482	$85.95	$85.95	$85.90
Purchase #3	$42.87	5.350%	$45.1635	$45.16	$45.15	$45.20
Purchase #4	$164.77	6.828%	$176.0205	$176.02	$176.00	$176.00
Purchase #5	$210.85	3.325%	$217.8608	$217.86	$217.85	$217.90
Purchase #6	$246.96	8.419%	$267.7516	$267.75	$267.75	$267.80
Purchase #7	$187.83	4.268%	$195.8466	$195.85	$195.85	$195.80
7 purchase totals =	$1,018.28		$1,078.4492	$1,078.45	$1,078.40	$1,078.50