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	$59.48	3.849%	$61.7694	$61.77	$61.75	$61.80
Purchase #2	$113.33	11.732%	$126.6259	$126.63	$126.65	$126.60
Purchase #3	$164.36	5.854%	$173.9816	$173.98	$174.00	$174.00
Purchase #4	$234.49	13.839%	$266.9411	$266.94	$266.95	$266.90
Purchase #5	$46.33	12.672%	$52.2009	$52.20	$52.20	$52.20
Purchase #6	$235.78	10.434%	$260.3813	$260.38	$260.40	$260.40
Purchase #7	$249.68	12.256%	$280.2808	$280.28	$280.30	$280.30
7 purchase totals =	$1,103.45		$1,222.1810	$1,222.18	$1,222.25	$1,222.20