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	$53.95	13.115%	$61.0255	$61.03	$61.05	$61.00
Purchase #2	$37.76	9.456%	$41.3306	$41.33	$41.35	$41.30
Purchase #3	$123.65	12.110%	$138.624	$138.62	$138.60	$138.60
Purchase #4	$5.98	5.677%	$6.3195	$6.32	$6.30	$6.30
Purchase #5	$38.54	9.567%	$42.2271	$42.23	$42.25	$42.20
Purchase #6	$233.49	9.605%	$255.9167	$255.92	$255.90	$255.90
Purchase #7	$34.27	9.469%	$37.515	$37.52	$37.50	$37.50
7 purchase totals =	$527.64		$582.9584	$582.97	$582.95	$582.80