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	$246.94	11.841%	$276.1802	$276.18	$276.20	$276.20
Purchase #2	$38.28	13.847%	$43.5806	$43.58	$43.60	$43.60
Purchase #3	$217.83	8.215%	$235.7247	$235.72	$235.70	$235.70
Purchase #4	$67.32	7.505%	$72.3724	$72.37	$72.35	$72.40
Purchase #5	$133.82	13.120%	$151.3772	$151.38	$151.40	$151.40
Purchase #6	$217.59	11.169%	$241.8926	$241.89	$241.90	$241.90
Purchase #7	$29.95	9.260%	$32.7234	$32.72	$32.70	$32.70
7 purchase totals =	$951.73		$1,053.8511	$1,053.84	$1,053.85	$1,053.90