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	$62.64	7.333%	$67.2334	$67.23	$67.25	$67.20
Purchase #2	$247.90	3.364%	$256.2394	$256.24	$256.25	$256.20
Purchase #3	$52.93	8.733%	$57.5524	$57.55	$57.55	$57.60
Purchase #4	$177.46	4.622%	$185.6622	$185.66	$185.65	$185.70
Purchase #5	$224.27	3.170%	$231.3794	$231.38	$231.40	$231.40
Purchase #6	$38.67	9.155%	$42.2102	$42.21	$42.20	$42.20
Purchase #7	$6.28	4.108%	$6.538	$6.54	$6.55	$6.50
7 purchase totals =	$810.15		$846.8150	$846.81	$846.85	$846.80