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	$98.74	6.800%	$105.4543	$105.45	$105.45	$105.50
Purchase #2	$241.26	11.109%	$268.0616	$268.06	$268.05	$268.10
Purchase #3	$101.81	7.398%	$109.3419	$109.34	$109.35	$109.30
Purchase #4	$51.58	5.554%	$54.4448	$54.44	$54.45	$54.40
Purchase #5	$54.75	3.594%	$56.7177	$56.72	$56.70	$56.70
Purchase #6	$191.90	8.649%	$208.4974	$208.50	$208.50	$208.50
Purchase #7	$39.43	6.741%	$42.088	$42.09	$42.10	$42.10
7 purchase totals =	$779.47		$844.6057	$844.60	$844.60	$844.60