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	$127.61	4.869%	$133.8233	$133.82	$133.80	$133.80
Purchase #2	$129.26	10.252%	$142.5117	$142.51	$142.50	$142.50
Purchase #3	$127.88	13.840%	$145.5786	$145.58	$145.60	$145.60
Purchase #4	$233.74	10.528%	$258.3481	$258.35	$258.35	$258.30
Purchase #5	$16.64	4.278%	$17.3519	$17.35	$17.35	$17.40
Purchase #6	$111.30	9.624%	$122.0115	$122.01	$122.00	$122.00
Purchase #7	$189.54	3.484%	$196.1436	$196.14	$196.15	$196.10
7 purchase totals =	$935.97		$1,015.7687	$1,015.76	$1,015.75	$1,015.70