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	$189.71	13.401%	$215.133	$215.13	$215.15	$215.10
Purchase #2	$114.81	7.260%	$123.1452	$123.15	$123.15	$123.10
Purchase #3	$242.93	12.332%	$272.8881	$272.89	$272.90	$272.90
Purchase #4	$56.81	10.541%	$62.7983	$62.80	$62.80	$62.80
Purchase #5	$195.83	7.653%	$210.8169	$210.82	$210.80	$210.80
Purchase #6	$113.66	10.394%	$125.4738	$125.47	$125.45	$125.50
Purchase #7	$147.62	5.395%	$155.5841	$155.58	$155.60	$155.60
7 purchase totals =	$1,061.37		$1,165.8394	$1,165.84	$1,165.85	$1,165.80