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	$15.72	4.658%	$16.4522	$16.45	$16.45	$16.50
Purchase #2	$72.61	6.518%	$77.3427	$77.34	$77.35	$77.30
Purchase #3	$25.44	10.395%	$28.0845	$28.08	$28.10	$28.10
Purchase #4	$12.95	6.557%	$13.7991	$13.80	$13.80	$13.80
Purchase #5	$60.99	6.437%	$64.9159	$64.92	$64.90	$64.90
Purchase #6	$217.67	7.289%	$233.536	$233.54	$233.55	$233.50
Purchase #7	$214.51	8.666%	$233.0994	$233.10	$233.10	$233.10
7 purchase totals =	$619.89		$667.2298	$667.23	$667.25	$667.20