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	$101.36	3.806%	$105.2178	$105.22	$105.20	$105.20
Purchase #2	$155.42	7.138%	$166.5139	$166.51	$166.50	$166.50
Purchase #3	$58.54	5.746%	$61.9037	$61.90	$61.90	$61.90
Purchase #4	$66.91	12.494%	$75.2697	$75.27	$75.25	$75.30
Purchase #5	$173.65	13.776%	$197.572	$197.57	$197.55	$197.60
Purchase #6	$38.71	10.820%	$42.8984	$42.90	$42.90	$42.90
Purchase #7	$83.91	6.669%	$89.506	$89.51	$89.50	$89.50
7 purchase totals =	$678.50		$738.8815	$738.88	$738.80	$738.90