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	$38.64	13.760%	$43.9569	$43.96	$43.95	$44.00
Purchase #2	$22.71	10.345%	$25.0593	$25.06	$25.05	$25.10
Purchase #3	$75.49	4.559%	$78.9316	$78.93	$78.95	$78.90
Purchase #4	$57.78	3.413%	$59.752	$59.75	$59.75	$59.80
Purchase #5	$39.72	5.288%	$41.8204	$41.82	$41.80	$41.80
Purchase #6	$152.45	7.822%	$164.3746	$164.37	$164.35	$164.40
Purchase #7	$113.99	9.129%	$124.3961	$124.40	$124.40	$124.40
7 purchase totals =	$500.78		$538.2909	$538.29	$538.25	$538.40