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	$84.95	6.700%	$90.6417	$90.64	$90.65	$90.60
Purchase #2	$110.38	5.337%	$116.271	$116.27	$116.25	$116.30
Purchase #3	$95.66	5.113%	$100.5511	$100.55	$100.55	$100.60
Purchase #4	$17.71	3.280%	$18.2909	$18.29	$18.30	$18.30
Purchase #5	$52.61	3.301%	$54.3467	$54.35	$54.35	$54.30
Purchase #6	$107.66	6.217%	$114.3532	$114.35	$114.35	$114.40
Purchase #7	$44.83	13.726%	$50.9834	$50.98	$51.00	$51.00
7 purchase totals =	$513.80		$545.4380	$545.43	$545.45	$545.50