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	$199.61	4.462%	$208.5166	$208.52	$208.50	$208.50
Purchase #2	$14.34	8.743%	$15.5937	$15.59	$15.60	$15.60
Purchase #3	$187.64	13.339%	$212.6693	$212.67	$212.65	$212.70
Purchase #4	$142.83	11.587%	$159.3797	$159.38	$159.40	$159.40
Purchase #5	$99.98	5.112%	$105.091	$105.09	$105.10	$105.10
Purchase #6	$151.50	3.223%	$156.3828	$156.38	$156.40	$156.40
Purchase #7	$219.58	6.429%	$233.6968	$233.70	$233.70	$233.70
7 purchase totals =	$1,015.48		$1,091.3299	$1,091.33	$1,091.35	$1,091.40