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	$56.38	5.869%	$59.6889	$59.69	$59.70	$59.70
Purchase #2	$138.94	8.666%	$150.9805	$150.98	$151.00	$151.00
Purchase #3	$55.85	5.670%	$59.0167	$59.02	$59.00	$59.00
Purchase #4	$45.83	4.717%	$47.9918	$47.99	$48.00	$48.00
Purchase #5	$241.40	12.707%	$272.0747	$272.07	$272.05	$272.10
Purchase #6	$173.40	8.612%	$188.3332	$188.33	$188.35	$188.30
Purchase #7	$230.73	13.569%	$262.0378	$262.04	$262.05	$262.00
7 purchase totals =	$942.53		$1,040.1236	$1,040.12	$1,040.15	$1,040.10