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	$119.41	6.810%	$127.5418	$127.54	$127.55	$127.50
Purchase #2	$111.77	9.211%	$122.0651	$122.07	$122.05	$122.10
Purchase #3	$16.74	11.735%	$18.7044	$18.70	$18.70	$18.70
Purchase #4	$84.94	5.836%	$89.8971	$89.90	$89.90	$89.90
Purchase #5	$57.52	9.256%	$62.8441	$62.84	$62.85	$62.80
Purchase #6	$138.29	11.679%	$154.4409	$154.44	$154.45	$154.40
Purchase #7	$86.39	12.757%	$97.4108	$97.41	$97.40	$97.40
7 purchase totals =	$615.06		$672.9042	$672.90	$672.90	$672.80