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	$221.93	5.498%	$234.1317	$234.13	$234.15	$234.10
Purchase #2	$185.81	5.717%	$196.4328	$196.43	$196.45	$196.40
Purchase #3	$86.58	3.869%	$89.9298	$89.93	$89.95	$89.90
Purchase #4	$50.92	6.481%	$54.2201	$54.22	$54.20	$54.20
Purchase #5	$26.60	3.864%	$27.6278	$27.63	$27.65	$27.60
Purchase #6	$204.28	13.279%	$231.4063	$231.41	$231.40	$231.40
Purchase #7	$224.80	4.246%	$234.345	$234.35	$234.35	$234.30
7 purchase totals =	$1,000.92		$1,068.0935	$1,068.10	$1,068.15	$1,067.90