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	$143.50	13.272%	$162.5453	$162.55	$162.55	$162.50
Purchase #2	$46.33	10.810%	$51.3383	$51.34	$51.35	$51.30
Purchase #3	$136.53	6.771%	$145.7744	$145.77	$145.75	$145.80
Purchase #4	$240.46	8.166%	$260.096	$260.10	$260.10	$260.10
Purchase #5	$41.96	3.732%	$43.5259	$43.53	$43.55	$43.50
Purchase #6	$154.36	8.793%	$167.9329	$167.93	$167.95	$167.90
Purchase #7	$70.47	11.786%	$78.7756	$78.78	$78.80	$78.80
7 purchase totals =	$833.61		$909.9884	$910.00	$910.05	$909.90