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	$160.39	12.627%	$180.6424	$180.64	$180.65	$180.60
Purchase #2	$56.73	5.375%	$59.7792	$59.78	$59.80	$59.80
Purchase #3	$132.45	9.267%	$144.7241	$144.72	$144.70	$144.70
Purchase #4	$35.57	7.121%	$38.1029	$38.10	$38.10	$38.10
Purchase #5	$120.41	9.231%	$131.525	$131.53	$131.55	$131.50
Purchase #6	$118.53	13.126%	$134.0882	$134.09	$134.10	$134.10
Purchase #7	$20.29	5.847%	$21.4764	$21.48	$21.50	$21.50
7 purchase totals =	$644.37		$710.3382	$710.34	$710.40	$710.30