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	$105.37	3.609%	$109.1728	$109.17	$109.15	$109.20
Purchase #2	$73.26	11.344%	$81.5706	$81.57	$81.55	$81.60
Purchase #3	$158.38	9.319%	$173.1394	$173.14	$173.15	$173.10
Purchase #4	$174.54	3.469%	$180.5948	$180.59	$180.60	$180.60
Purchase #5	$149.76	10.766%	$165.8832	$165.88	$165.90	$165.90
Purchase #6	$204.94	9.373%	$224.149	$224.15	$224.15	$224.10
Purchase #7	$198.52	9.404%	$217.1888	$217.19	$217.20	$217.20
7 purchase totals =	$1,064.77		$1,151.6986	$1,151.69	$1,151.70	$1,151.70