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	$163.31	9.864%	$179.4189	$179.42	$179.40	$179.40
Purchase #2	$140.34	7.868%	$151.382	$151.38	$151.40	$151.40
Purchase #3	$179.98	10.637%	$199.1245	$199.12	$199.10	$199.10
Purchase #4	$132.31	6.109%	$140.3928	$140.39	$140.40	$140.40
Purchase #5	$86.38	13.282%	$97.853	$97.85	$97.85	$97.90
Purchase #6	$198.98	3.847%	$206.6348	$206.63	$206.65	$206.60
Purchase #7	$20.36	5.734%	$21.5274	$21.53	$21.55	$21.50
7 purchase totals =	$921.66		$996.3334	$996.32	$996.35	$996.30