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	$75.25	10.193%	$82.9202	$82.92	$82.90	$82.90
Purchase #2	$16.41	12.773%	$18.506	$18.51	$18.50	$18.50
Purchase #3	$125.55	4.839%	$131.6254	$131.63	$131.65	$131.60
Purchase #4	$21.79	12.323%	$24.4752	$24.48	$24.50	$24.50
Purchase #5	$208.36	10.805%	$230.8733	$230.87	$230.85	$230.90
Purchase #6	$70.76	9.386%	$77.4015	$77.40	$77.40	$77.40
Purchase #7	$37.66	3.113%	$38.8324	$38.83	$38.85	$38.80
7 purchase totals =	$555.78		$604.6340	$604.64	$604.65	$604.60