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	$97.66	13.809%	$111.1459	$111.15	$111.15	$111.10
Purchase #2	$20.54	6.549%	$21.8852	$21.89	$21.90	$21.90
Purchase #3	$235.72	12.636%	$265.5056	$265.51	$265.50	$265.50
Purchase #4	$156.97	6.320%	$166.8905	$166.89	$166.90	$166.90
Purchase #5	$231.42	6.226%	$245.8282	$245.83	$245.85	$245.80
Purchase #6	$176.76	10.540%	$195.3905	$195.39	$195.40	$195.40
Purchase #7	$134.57	7.517%	$144.6856	$144.69	$144.70	$144.70
7 purchase totals =	$1,053.64		$1,151.3315	$1,151.35	$1,151.40	$1,151.30