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	$238.94	7.295%	$256.3707	$256.37	$256.35	$256.40
Purchase #2	$244.34	5.546%	$257.8911	$257.89	$257.90	$257.90
Purchase #3	$19.82	12.736%	$22.3443	$22.34	$22.35	$22.30
Purchase #4	$100.66	8.804%	$109.5221	$109.52	$109.50	$109.50
Purchase #5	$197.97	10.189%	$218.1412	$218.14	$218.15	$218.10
Purchase #6	$36.33	4.274%	$37.8827	$37.88	$37.90	$37.90
Purchase #7	$217.61	10.332%	$240.0935	$240.09	$240.10	$240.10
7 purchase totals =	$1,055.67		$1,142.2456	$1,142.23	$1,142.25	$1,142.20