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	$128.66	10.624%	$142.3288	$142.33	$142.35	$142.30
Purchase #2	$237.60	10.612%	$262.8141	$262.81	$262.80	$262.80
Purchase #3	$16.73	4.852%	$17.5417	$17.54	$17.55	$17.50
Purchase #4	$55.45	7.747%	$59.7457	$59.75	$59.75	$59.70
Purchase #5	$90.57	3.243%	$93.5072	$93.51	$93.50	$93.50
Purchase #6	$149.39	8.511%	$162.1046	$162.10	$162.10	$162.10
Purchase #7	$43.43	10.703%	$48.0783	$48.08	$48.10	$48.10
7 purchase totals =	$721.83		$786.1204	$786.12	$786.15	$786.00