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	$210.78	10.671%	$233.2723	$233.27	$233.25	$233.30
Purchase #2	$60.65	7.389%	$65.1314	$65.13	$65.15	$65.10
Purchase #3	$224.43	7.200%	$240.589	$240.59	$240.60	$240.60
Purchase #4	$72.67	3.121%	$74.938	$74.94	$74.95	$74.90
Purchase #5	$86.48	5.435%	$91.1802	$91.18	$91.20	$91.20
Purchase #6	$55.45	4.218%	$57.7889	$57.79	$57.80	$57.80
Purchase #7	$160.72	12.510%	$180.8261	$180.83	$180.85	$180.80
7 purchase totals =	$871.18		$943.7259	$943.73	$943.80	$943.70