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	$163.39	6.404%	$173.8535	$173.85	$173.85	$173.90
Purchase #2	$16.32	9.161%	$17.8151	$17.82	$17.80	$17.80
Purchase #3	$240.54	6.681%	$256.6105	$256.61	$256.60	$256.60
Purchase #4	$227.33	6.772%	$242.7248	$242.72	$242.70	$242.70
Purchase #5	$39.57	7.531%	$42.55	$42.55	$42.55	$42.60
Purchase #6	$21.45	9.342%	$23.4539	$23.45	$23.45	$23.50
Purchase #7	$240.75	4.180%	$250.8134	$250.81	$250.80	$250.80
7 purchase totals =	$949.35		$1,007.8212	$1,007.81	$1,007.75	$1,007.90