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	$52.41	4.334%	$54.6814	$54.68	$54.70	$54.70
Purchase #2	$17.52	7.740%	$18.876	$18.88	$18.90	$18.90
Purchase #3	$208.83	10.401%	$230.5504	$230.55	$230.55	$230.60
Purchase #4	$84.96	6.843%	$90.7738	$90.77	$90.75	$90.80
Purchase #5	$238.81	4.256%	$248.9738	$248.97	$248.95	$249.00
Purchase #6	$220.51	7.558%	$237.1761	$237.18	$237.20	$237.20
Purchase #7	$183.62	9.395%	$200.8711	$200.87	$200.85	$200.90
7 purchase totals =	$1,006.66		$1,081.9026	$1,081.90	$1,081.90	$1,082.10