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	$150.32	8.410%	$162.9619	$162.96	$162.95	$163.00
Purchase #2	$150.84	9.861%	$165.7143	$165.71	$165.70	$165.70
Purchase #3	$86.45	10.768%	$95.7589	$95.76	$95.75	$95.80
Purchase #4	$13.59	3.470%	$14.0616	$14.06	$14.05	$14.10
Purchase #5	$180.83	8.613%	$196.4049	$196.40	$196.40	$196.40
Purchase #6	$34.27	10.549%	$37.8851	$37.89	$37.90	$37.90
Purchase #7	$172.92	11.580%	$192.9441	$192.94	$192.95	$192.90
7 purchase totals =	$789.22		$865.7308	$865.72	$865.70	$865.80