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	$186.33	3.426%	$192.7137	$192.71	$192.70	$192.70
Purchase #2	$17.91	3.349%	$18.5098	$18.51	$18.50	$18.50
Purchase #3	$138.76	5.861%	$146.8927	$146.89	$146.90	$146.90
Purchase #4	$211.85	4.544%	$221.4765	$221.48	$221.50	$221.50
Purchase #5	$80.70	4.819%	$84.5889	$84.59	$84.60	$84.60
Purchase #6	$104.28	8.589%	$113.2366	$113.24	$113.25	$113.20
Purchase #7	$68.51	5.785%	$72.4733	$72.47	$72.45	$72.50
7 purchase totals =	$808.34		$849.8915	$849.89	$849.90	$849.90