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	$43.78	5.783%	$46.3118	$46.31	$46.30	$46.30
Purchase #2	$60.67	5.387%	$63.9383	$63.94	$63.95	$63.90
Purchase #3	$191.41	4.145%	$199.3439	$199.34	$199.35	$199.30
Purchase #4	$175.40	12.192%	$196.7848	$196.78	$196.80	$196.80
Purchase #5	$151.98	13.492%	$172.4851	$172.49	$172.50	$172.50
Purchase #6	$112.42	9.858%	$123.5024	$123.50	$123.50	$123.50
Purchase #7	$10.42	7.646%	$11.2167	$11.22	$11.20	$11.20
7 purchase totals =	$746.08		$813.5830	$813.58	$813.60	$813.50