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	$99.71	7.282%	$106.9709	$106.97	$106.95	$107.00
Purchase #2	$168.31	9.871%	$184.9239	$184.92	$184.90	$184.90
Purchase #3	$11.53	6.233%	$12.2487	$12.25	$12.25	$12.20
Purchase #4	$142.35	8.792%	$154.8654	$154.87	$154.85	$154.90
Purchase #5	$152.49	13.190%	$172.6034	$172.60	$172.60	$172.60
Purchase #6	$176.35	4.292%	$183.9189	$183.92	$183.90	$183.90
Purchase #7	$52.71	12.859%	$59.488	$59.49	$59.50	$59.50
7 purchase totals =	$803.45		$875.0192	$875.02	$874.95	$875.00