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	$160.90	7.838%	$173.5113	$173.51	$173.50	$173.50
Purchase #2	$23.39	13.690%	$26.5921	$26.59	$26.60	$26.60
Purchase #3	$162.54	6.749%	$173.5098	$173.51	$173.50	$173.50
Purchase #4	$122.32	8.428%	$132.6291	$132.63	$132.65	$132.60
Purchase #5	$187.42	12.250%	$210.379	$210.38	$210.40	$210.40
Purchase #6	$249.66	12.862%	$281.7713	$281.77	$281.75	$281.80
Purchase #7	$71.50	9.386%	$78.211	$78.21	$78.20	$78.20
7 purchase totals =	$977.73		$1,076.6036	$1,076.60	$1,076.60	$1,076.60