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	$213.86	8.291%	$231.5911	$231.59	$231.60	$231.60
Purchase #2	$78.57	4.670%	$82.2392	$82.24	$82.25	$82.20
Purchase #3	$57.40	11.500%	$64.001	$64.00	$64.00	$64.00
Purchase #4	$18.91	7.693%	$20.3647	$20.36	$20.35	$20.40
Purchase #5	$137.87	11.314%	$153.4686	$153.47	$153.45	$153.50
Purchase #6	$176.64	13.206%	$199.9671	$199.97	$199.95	$200.00
Purchase #7	$240.82	13.488%	$273.3018	$273.30	$273.30	$273.30
7 purchase totals =	$924.07		$1,024.9335	$1,024.93	$1,024.90	$1,025.00