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	$99.47	8.847%	$108.2701	$108.27	$108.25	$108.30
Purchase #2	$71.63	13.627%	$81.391	$81.39	$81.40	$81.40
Purchase #3	$225.51	10.117%	$248.3248	$248.32	$248.30	$248.30
Purchase #4	$38.45	5.683%	$40.6351	$40.64	$40.65	$40.60
Purchase #5	$167.89	3.316%	$173.4572	$173.46	$173.45	$173.50
Purchase #6	$53.79	10.664%	$59.5262	$59.53	$59.55	$59.50
Purchase #7	$150.77	6.141%	$160.0288	$160.03	$160.05	$160.00
7 purchase totals =	$807.51		$871.6332	$871.64	$871.65	$871.60