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	$111.70	5.326%	$117.6491	$117.65	$117.65	$117.60
Purchase #2	$12.67	10.406%	$13.9884	$13.99	$14.00	$14.00
Purchase #3	$32.34	4.384%	$33.7578	$33.76	$33.75	$33.80
Purchase #4	$41.85	6.199%	$44.4443	$44.44	$44.45	$44.40
Purchase #5	$20.32	6.235%	$21.587	$21.59	$21.60	$21.60
Purchase #6	$212.84	9.738%	$233.5664	$233.57	$233.55	$233.60
Purchase #7	$32.32	3.232%	$33.3646	$33.36	$33.35	$33.40
7 purchase totals =	$464.04		$498.3576	$498.36	$498.35	$498.40