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	$150.85	10.715%	$167.0136	$167.01	$167.00	$167.00
Purchase #2	$143.64	9.132%	$156.7572	$156.76	$156.75	$156.80
Purchase #3	$54.62	4.617%	$57.1418	$57.14	$57.15	$57.10
Purchase #4	$97.71	13.872%	$111.2643	$111.26	$111.25	$111.30
Purchase #5	$22.41	10.821%	$24.835	$24.84	$24.85	$24.80
Purchase #6	$127.95	9.766%	$140.4456	$140.45	$140.45	$140.40
Purchase #7	$175.38	10.387%	$193.5967	$193.60	$193.60	$193.60
7 purchase totals =	$772.56		$851.0542	$851.06	$851.05	$851.00