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	$128.88	9.458%	$141.0695	$141.07	$141.05	$141.10
Purchase #2	$178.37	8.863%	$194.1789	$194.18	$194.20	$194.20
Purchase #3	$138.76	5.432%	$146.2974	$146.30	$146.30	$146.30
Purchase #4	$100.40	8.722%	$109.1569	$109.16	$109.15	$109.20
Purchase #5	$52.32	11.839%	$58.5142	$58.51	$58.50	$58.50
Purchase #6	$52.56	13.371%	$59.5878	$59.59	$59.60	$59.60
Purchase #7	$205.73	4.495%	$214.9776	$214.98	$215.00	$215.00
7 purchase totals =	$857.02		$923.7823	$923.79	$923.80	$923.90