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	$149.35	7.450%	$160.4766	$160.48	$160.50	$160.50
Purchase #2	$233.93	13.872%	$266.3808	$266.38	$266.40	$266.40
Purchase #3	$156.60	10.143%	$172.4839	$172.48	$172.50	$172.50
Purchase #4	$134.83	10.379%	$148.824	$148.82	$148.80	$148.80
Purchase #5	$50.89	3.521%	$52.6818	$52.68	$52.70	$52.70
Purchase #6	$36.41	12.551%	$40.9798	$40.98	$41.00	$41.00
Purchase #7	$181.74	12.618%	$204.672	$204.67	$204.65	$204.70
7 purchase totals =	$943.75		$1,046.4989	$1,046.49	$1,046.55	$1,046.60