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	$126.99	9.315%	$138.8191	$138.82	$138.80	$138.80
Purchase #2	$186.95	13.714%	$212.5883	$212.59	$212.60	$212.60
Purchase #3	$71.45	10.303%	$78.8115	$78.81	$78.80	$78.80
Purchase #4	$156.32	3.759%	$162.1961	$162.20	$162.20	$162.20
Purchase #5	$32.99	13.431%	$37.4209	$37.42	$37.40	$37.40
Purchase #6	$151.43	10.537%	$167.3862	$167.39	$167.40	$167.40
Purchase #7	$163.60	9.596%	$179.2991	$179.30	$179.30	$179.30
7 purchase totals =	$889.73		$976.5212	$976.53	$976.50	$976.50