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	$57.54	4.463%	$60.108	$60.11	$60.10	$60.10
Purchase #2	$42.43	4.821%	$44.4756	$44.48	$44.50	$44.50
Purchase #3	$95.32	10.455%	$105.2857	$105.29	$105.30	$105.30
Purchase #4	$121.78	8.839%	$132.5441	$132.54	$132.55	$132.50
Purchase #5	$200.83	5.745%	$212.3677	$212.37	$212.35	$212.40
Purchase #6	$134.67	9.249%	$147.1256	$147.13	$147.15	$147.10
Purchase #7	$188.38	5.347%	$198.4527	$198.45	$198.45	$198.50
7 purchase totals =	$840.95		$900.3594	$900.37	$900.40	$900.40