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	$233.65	13.244%	$264.5946	$264.59	$264.60	$264.60
Purchase #2	$130.85	13.830%	$148.9466	$148.95	$148.95	$148.90
Purchase #3	$100.50	10.860%	$111.4143	$111.41	$111.40	$111.40
Purchase #4	$168.68	6.323%	$179.3456	$179.35	$179.35	$179.30
Purchase #5	$34.98	5.543%	$36.9189	$36.92	$36.90	$36.90
Purchase #6	$214.37	12.668%	$241.5264	$241.53	$241.55	$241.50
Purchase #7	$93.46	12.423%	$105.0705	$105.07	$105.05	$105.10
7 purchase totals =	$976.49		$1,087.8169	$1,087.82	$1,087.80	$1,087.70