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	$60.28	8.129%	$65.1802	$65.18	$65.20	$65.20
Purchase #2	$105.89	11.828%	$118.4147	$118.41	$118.40	$118.40
Purchase #3	$177.99	12.851%	$200.8635	$200.86	$200.85	$200.90
Purchase #4	$51.84	3.230%	$53.5144	$53.51	$53.50	$53.50
Purchase #5	$73.85	12.671%	$83.2075	$83.21	$83.20	$83.20
Purchase #6	$140.78	7.651%	$151.5511	$151.55	$151.55	$151.60
Purchase #7	$210.25	7.449%	$225.9115	$225.91	$225.90	$225.90
7 purchase totals =	$820.88		$898.6429	$898.63	$898.60	$898.70