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	$62.34	6.463%	$66.369	$66.37	$66.35	$66.40
Purchase #2	$28.25	3.363%	$29.2	$29.20	$29.20	$29.20
Purchase #3	$228.47	12.411%	$256.8254	$256.83	$256.85	$256.80
Purchase #4	$111.65	10.225%	$123.0662	$123.07	$123.05	$123.10
Purchase #5	$205.65	12.571%	$231.5023	$231.50	$231.50	$231.50
Purchase #6	$172.56	7.855%	$186.1146	$186.11	$186.10	$186.10
Purchase #7	$153.72	7.279%	$164.9093	$164.91	$164.90	$164.90
7 purchase totals =	$962.64		$1,057.9868	$1,057.99	$1,057.95	$1,058.00