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	$83.90	8.159%	$90.7454	$90.75	$90.75	$90.70
Purchase #2	$231.27	5.233%	$243.3724	$243.37	$243.35	$243.40
Purchase #3	$40.81	12.582%	$45.9447	$45.94	$45.95	$45.90
Purchase #4	$39.58	9.781%	$43.4513	$43.45	$43.45	$43.50
Purchase #5	$124.27	10.209%	$136.9567	$136.96	$136.95	$137.00
Purchase #6	$238.31	5.836%	$252.2178	$252.22	$252.20	$252.20
Purchase #7	$212.72	9.649%	$233.2454	$233.25	$233.25	$233.20
7 purchase totals =	$970.86		$1,045.9337	$1,045.94	$1,045.90	$1,045.90