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	$54.75	7.841%	$59.0429	$59.04	$59.05	$59.00
Purchase #2	$212.77	10.318%	$234.7236	$234.72	$234.70	$234.70
Purchase #3	$37.97	11.380%	$42.291	$42.29	$42.30	$42.30
Purchase #4	$92.43	8.653%	$100.428	$100.43	$100.45	$100.40
Purchase #5	$111.78	9.177%	$122.0381	$122.04	$122.05	$122.00
Purchase #6	$115.34	6.660%	$123.0216	$123.02	$123.00	$123.00
Purchase #7	$78.39	5.861%	$82.9844	$82.98	$83.00	$83.00
7 purchase totals =	$703.43		$764.5296	$764.52	$764.55	$764.40