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	$150.73	3.763%	$156.402	$156.40	$156.40	$156.40
Purchase #2	$105.75	6.760%	$112.8987	$112.90	$112.90	$112.90
Purchase #3	$64.95	3.662%	$67.3285	$67.33	$67.35	$67.30
Purchase #4	$216.63	3.440%	$224.0821	$224.08	$224.10	$224.10
Purchase #5	$215.54	9.252%	$235.4818	$235.48	$235.50	$235.50
Purchase #6	$70.87	11.383%	$78.9371	$78.94	$78.95	$78.90
Purchase #7	$154.28	9.235%	$168.5278	$168.53	$168.55	$168.50
7 purchase totals =	$978.75		$1,043.6580	$1,043.66	$1,043.75	$1,043.60