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	$82.70	8.697%	$89.8924	$89.89	$89.90	$89.90
Purchase #2	$104.44	3.405%	$107.9962	$108.00	$108.00	$108.00
Purchase #3	$71.66	4.404%	$74.8159	$74.82	$74.80	$74.80
Purchase #4	$121.35	4.834%	$127.2161	$127.22	$127.20	$127.20
Purchase #5	$194.53	12.346%	$218.5467	$218.55	$218.55	$218.50
Purchase #6	$178.81	5.743%	$189.0791	$189.08	$189.10	$189.10
Purchase #7	$82.89	9.718%	$90.9453	$90.95	$90.95	$90.90
7 purchase totals =	$836.38		$898.4917	$898.51	$898.50	$898.40