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	$206.40	13.581%	$234.4312	$234.43	$234.45	$234.40
Purchase #2	$153.44	9.781%	$168.448	$168.45	$168.45	$168.40
Purchase #3	$78.54	9.481%	$85.9864	$85.99	$86.00	$86.00
Purchase #4	$134.31	10.733%	$148.7255	$148.73	$148.75	$148.70
Purchase #5	$99.87	6.307%	$106.1688	$106.17	$106.15	$106.20
Purchase #6	$175.55	13.112%	$198.5681	$198.57	$198.55	$198.60
Purchase #7	$141.72	6.724%	$151.2493	$151.25	$151.25	$151.20
7 purchase totals =	$989.83		$1,093.5773	$1,093.59	$1,093.60	$1,093.50