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	$97.43	8.512%	$105.7232	$105.72	$105.70	$105.70
Purchase #2	$142.73	10.447%	$157.641	$157.64	$157.65	$157.60
Purchase #3	$159.54	6.838%	$170.4493	$170.45	$170.45	$170.40
Purchase #4	$37.89	5.822%	$40.096	$40.10	$40.10	$40.10
Purchase #5	$185.27	12.513%	$208.4528	$208.45	$208.45	$208.50
Purchase #6	$179.38	3.487%	$185.635	$185.64	$185.65	$185.60
Purchase #7	$89.63	12.802%	$101.1044	$101.10	$101.10	$101.10
7 purchase totals =	$891.87		$969.1017	$969.10	$969.10	$969.00