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	$232.93	6.369%	$247.7653	$247.77	$247.75	$247.80
Purchase #2	$129.39	6.509%	$137.812	$137.81	$137.80	$137.80
Purchase #3	$89.31	3.664%	$92.5823	$92.58	$92.60	$92.60
Purchase #4	$57.37	3.257%	$59.2385	$59.24	$59.25	$59.20
Purchase #5	$140.57	9.852%	$154.419	$154.42	$154.40	$154.40
Purchase #6	$223.27	8.760%	$242.8285	$242.83	$242.85	$242.80
Purchase #7	$181.45	5.708%	$191.8072	$191.81	$191.80	$191.80
7 purchase totals =	$1,054.29		$1,126.4528	$1,126.46	$1,126.45	$1,126.40