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	$128.95	12.822%	$145.484	$145.48	$145.50	$145.50
Purchase #2	$56.73	8.293%	$61.4346	$61.43	$61.45	$61.40
Purchase #3	$248.43	9.151%	$271.1638	$271.16	$271.15	$271.20
Purchase #4	$205.41	4.183%	$214.0023	$214.00	$214.00	$214.00
Purchase #5	$19.84	8.154%	$21.4578	$21.46	$21.45	$21.50
Purchase #6	$82.90	4.565%	$86.6844	$86.68	$86.70	$86.70
Purchase #7	$76.72	7.324%	$82.339	$82.34	$82.35	$82.30
7 purchase totals =	$818.98		$882.5659	$882.55	$882.60	$882.60