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	$178.98	6.546%	$190.696	$190.70	$190.70	$190.70
Purchase #2	$42.52	9.665%	$46.6296	$46.63	$46.65	$46.60
Purchase #3	$43.40	4.772%	$45.471	$45.47	$45.45	$45.50
Purchase #4	$93.40	6.455%	$99.429	$99.43	$99.45	$99.40
Purchase #5	$122.94	4.294%	$128.219	$128.22	$128.20	$128.20
Purchase #6	$57.49	9.872%	$63.1654	$63.17	$63.15	$63.20
Purchase #7	$149.64	11.241%	$166.461	$166.46	$166.45	$166.50
7 purchase totals =	$688.37		$740.0710	$740.08	$740.05	$740.10