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	$236.34	4.526%	$247.0367	$247.04	$247.05	$247.00
Purchase #2	$57.69	8.324%	$62.4921	$62.49	$62.50	$62.50
Purchase #3	$88.59	12.745%	$99.8808	$99.88	$99.90	$99.90
Purchase #4	$203.66	6.667%	$217.238	$217.24	$217.25	$217.20
Purchase #5	$26.25	13.493%	$29.7919	$29.79	$29.80	$29.80
Purchase #6	$231.38	6.255%	$245.8528	$245.85	$245.85	$245.90
Purchase #7	$178.67	3.759%	$185.3862	$185.39	$185.40	$185.40
7 purchase totals =	$1,022.58		$1,087.6785	$1,087.68	$1,087.75	$1,087.70