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	$100.87	10.116%	$111.074	$111.07	$111.05	$111.10
Purchase #2	$56.72	8.135%	$61.3342	$61.33	$61.35	$61.30
Purchase #3	$66.75	12.688%	$75.2192	$75.22	$75.20	$75.20
Purchase #4	$167.64	9.531%	$183.6178	$183.62	$183.60	$183.60
Purchase #5	$121.43	4.759%	$127.2089	$127.21	$127.20	$127.20
Purchase #6	$45.58	9.557%	$49.9361	$49.94	$49.95	$49.90
Purchase #7	$234.32	5.801%	$247.9129	$247.91	$247.90	$247.90
7 purchase totals =	$793.31		$856.3031	$856.30	$856.25	$856.20