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	$53.96	10.586%	$59.6722	$59.67	$59.65	$59.70
Purchase #2	$230.67	10.338%	$254.5167	$254.52	$254.50	$254.50
Purchase #3	$108.25	10.384%	$119.4907	$119.49	$119.50	$119.50
Purchase #4	$207.81	8.860%	$226.222	$226.22	$226.20	$226.20
Purchase #5	$109.33	7.822%	$117.8818	$117.88	$117.90	$117.90
Purchase #6	$122.59	7.243%	$131.4692	$131.47	$131.45	$131.50
Purchase #7	$159.43	5.334%	$167.934	$167.93	$167.95	$167.90
7 purchase totals =	$992.04		$1,077.1866	$1,077.18	$1,077.15	$1,077.20