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	$11.59	5.617%	$12.241	$12.24	$12.25	$12.20
Purchase #2	$179.27	8.537%	$194.5743	$194.57	$194.55	$194.60
Purchase #3	$214.59	12.138%	$240.6369	$240.64	$240.65	$240.60
Purchase #4	$189.48	5.287%	$199.4978	$199.50	$199.50	$199.50
Purchase #5	$59.84	11.777%	$66.8874	$66.89	$66.90	$66.90
Purchase #6	$113.25	4.754%	$118.6339	$118.63	$118.65	$118.60
Purchase #7	$165.33	10.142%	$182.0978	$182.10	$182.10	$182.10
7 purchase totals =	$933.35		$1,014.5691	$1,014.57	$1,014.60	$1,014.50