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	$249.72	3.497%	$258.4527	$258.45	$258.45	$258.50
Purchase #2	$60.95	10.172%	$67.1498	$67.15	$67.15	$67.10
Purchase #3	$39.37	5.396%	$41.4944	$41.49	$41.50	$41.50
Purchase #4	$233.45	6.175%	$247.8655	$247.87	$247.85	$247.90
Purchase #5	$247.55	6.736%	$264.225	$264.23	$264.25	$264.20
Purchase #6	$121.51	9.337%	$132.8554	$132.86	$132.85	$132.90
Purchase #7	$11.69	13.805%	$13.3038	$13.30	$13.30	$13.30
7 purchase totals =	$964.24		$1,025.3466	$1,025.35	$1,025.35	$1,025.40