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	$230.69	6.784%	$246.34	$246.34	$246.35	$246.30
Purchase #2	$50.28	7.172%	$53.8861	$53.89	$53.90	$53.90
Purchase #3	$56.37	6.110%	$59.8142	$59.81	$59.80	$59.80
Purchase #4	$36.41	9.597%	$39.9043	$39.90	$39.90	$39.90
Purchase #5	$111.97	4.153%	$116.6201	$116.62	$116.60	$116.60
Purchase #6	$145.31	13.586%	$165.0518	$165.05	$165.05	$165.10
Purchase #7	$112.33	6.448%	$119.573	$119.57	$119.55	$119.60
7 purchase totals =	$743.36		$801.1895	$801.18	$801.15	$801.20