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	$140.98	6.572%	$150.2452	$150.25	$150.25	$150.20
Purchase #2	$53.72	6.578%	$57.2537	$57.25	$57.25	$57.30
Purchase #3	$136.86	8.538%	$148.5451	$148.55	$148.55	$148.50
Purchase #4	$100.44	4.772%	$105.233	$105.23	$105.25	$105.20
Purchase #5	$138.83	5.476%	$146.4323	$146.43	$146.45	$146.40
Purchase #6	$162.52	5.395%	$171.288	$171.29	$171.30	$171.30
Purchase #7	$95.60	8.477%	$103.704	$103.70	$103.70	$103.70
7 purchase totals =	$828.95		$882.7013	$882.70	$882.75	$882.60