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	$239.42	3.271%	$247.2514	$247.25	$247.25	$247.30
Purchase #2	$28.39	12.446%	$31.9234	$31.92	$31.90	$31.90
Purchase #3	$227.89	3.333%	$235.4856	$235.49	$235.50	$235.50
Purchase #4	$193.81	6.210%	$205.8456	$205.85	$205.85	$205.80
Purchase #5	$186.45	7.769%	$200.9353	$200.94	$200.95	$200.90
Purchase #6	$72.92	5.460%	$76.9014	$76.90	$76.90	$76.90
Purchase #7	$129.59	11.790%	$144.8687	$144.87	$144.85	$144.90
7 purchase totals =	$1,078.47		$1,143.2114	$1,143.22	$1,143.20	$1,143.20