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	$160.70	5.425%	$169.418	$169.42	$169.40	$169.40
Purchase #2	$112.31	13.334%	$127.2854	$127.29	$127.30	$127.30
Purchase #3	$62.98	6.819%	$67.2746	$67.27	$67.25	$67.30
Purchase #4	$9.25	12.873%	$10.4408	$10.44	$10.45	$10.40
Purchase #5	$108.78	10.127%	$119.7962	$119.80	$119.80	$119.80
Purchase #6	$247.82	10.137%	$272.9415	$272.94	$272.95	$272.90
Purchase #7	$145.71	6.651%	$155.4012	$155.40	$155.40	$155.40
7 purchase totals =	$847.55		$922.5577	$922.56	$922.55	$922.50