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	$54.33	12.540%	$61.143	$61.14	$61.15	$61.10
Purchase #2	$27.54	3.575%	$28.5246	$28.52	$28.50	$28.50
Purchase #3	$234.83	9.385%	$256.8688	$256.87	$256.85	$256.90
Purchase #4	$246.57	5.246%	$259.5051	$259.51	$259.50	$259.50
Purchase #5	$44.67	3.464%	$46.2174	$46.22	$46.20	$46.20
Purchase #6	$208.54	8.563%	$226.3973	$226.40	$226.40	$226.40
Purchase #7	$129.79	6.724%	$138.5171	$138.52	$138.50	$138.50
7 purchase totals =	$946.27		$1,017.1733	$1,017.18	$1,017.10	$1,017.10