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	$67.37	7.649%	$72.5231	$72.52	$72.50	$72.50
Purchase #2	$89.79	3.631%	$93.0503	$93.05	$93.05	$93.10
Purchase #3	$194.40	3.728%	$201.6472	$201.65	$201.65	$201.60
Purchase #4	$139.38	11.114%	$154.8707	$154.87	$154.85	$154.90
Purchase #5	$28.44	13.540%	$32.2908	$32.29	$32.30	$32.30
Purchase #6	$239.32	9.513%	$262.0865	$262.09	$262.10	$262.10
Purchase #7	$88.36	13.598%	$100.3752	$100.38	$100.40	$100.40
7 purchase totals =	$847.06		$916.8438	$916.85	$916.85	$916.90