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	$54.25	10.191%	$59.7786	$59.78	$59.80	$59.80
Purchase #2	$128.62	13.631%	$146.1522	$146.15	$146.15	$146.20
Purchase #3	$204.47	7.102%	$218.9915	$218.99	$219.00	$219.00
Purchase #4	$38.39	8.403%	$41.6159	$41.62	$41.60	$41.60
Purchase #5	$157.78	11.257%	$175.5413	$175.54	$175.55	$175.50
Purchase #6	$222.83	4.828%	$233.5882	$233.59	$233.60	$233.60
Purchase #7	$153.93	11.156%	$171.1024	$171.10	$171.10	$171.10
7 purchase totals =	$960.27		$1,046.7701	$1,046.77	$1,046.80	$1,046.80