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	$85.38	5.358%	$89.9547	$89.95	$89.95	$90.00
Purchase #2	$89.64	13.839%	$102.0453	$102.05	$102.05	$102.00
Purchase #3	$106.32	9.637%	$116.5661	$116.57	$116.55	$116.60
Purchase #4	$155.61	5.432%	$164.0627	$164.06	$164.05	$164.10
Purchase #5	$137.34	7.583%	$147.7545	$147.75	$147.75	$147.80
Purchase #6	$12.65	10.323%	$13.9559	$13.96	$13.95	$14.00
Purchase #7	$76.73	4.403%	$80.1084	$80.11	$80.10	$80.10
7 purchase totals =	$663.67		$714.4476	$714.45	$714.40	$714.60