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	$169.29	13.142%	$191.5381	$191.54	$191.55	$191.50
Purchase #2	$136.76	13.164%	$154.7631	$154.76	$154.75	$154.80
Purchase #3	$55.61	12.815%	$62.7364	$62.74	$62.75	$62.70
Purchase #4	$39.86	13.579%	$45.2726	$45.27	$45.25	$45.30
Purchase #5	$49.60	3.660%	$51.4154	$51.42	$51.40	$51.40
Purchase #6	$245.26	12.410%	$275.6968	$275.70	$275.70	$275.70
Purchase #7	$123.47	4.427%	$128.936	$128.94	$128.95	$128.90
7 purchase totals =	$819.85		$910.3584	$910.37	$910.35	$910.30