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	$37.39	10.363%	$41.2647	$41.26	$41.25	$41.30
Purchase #2	$100.31	12.533%	$112.8819	$112.88	$112.90	$112.90
Purchase #3	$185.31	4.585%	$193.8065	$193.81	$193.80	$193.80
Purchase #4	$122.74	6.848%	$131.1452	$131.15	$131.15	$131.10
Purchase #5	$221.59	5.736%	$234.3004	$234.30	$234.30	$234.30
Purchase #6	$176.49	5.333%	$185.9022	$185.90	$185.90	$185.90
Purchase #7	$158.40	7.462%	$170.2198	$170.22	$170.20	$170.20
7 purchase totals =	$1,002.23		$1,069.5207	$1,069.52	$1,069.50	$1,069.50