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	$161.66	12.522%	$181.9031	$181.90	$181.90	$181.90
Purchase #2	$18.40	4.593%	$19.2451	$19.25	$19.25	$19.20
Purchase #3	$54.90	9.195%	$59.9481	$59.95	$59.95	$59.90
Purchase #4	$206.52	12.207%	$231.7299	$231.73	$231.75	$231.70
Purchase #5	$205.77	13.358%	$233.2568	$233.26	$233.25	$233.30
Purchase #6	$213.33	13.688%	$242.5306	$242.53	$242.55	$242.50
Purchase #7	$187.88	12.727%	$211.7915	$211.79	$211.80	$211.80
7 purchase totals =	$1,048.46		$1,180.4051	$1,180.41	$1,180.45	$1,180.30