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	$246.95	8.762%	$268.5878	$268.59	$268.60	$268.60
Purchase #2	$163.95	4.738%	$171.718	$171.72	$171.70	$171.70
Purchase #3	$168.29	6.164%	$178.6634	$178.66	$178.65	$178.70
Purchase #4	$105.72	11.525%	$117.9042	$117.90	$117.90	$117.90
Purchase #5	$50.57	11.802%	$56.5383	$56.54	$56.55	$56.50
Purchase #6	$153.91	9.717%	$168.8654	$168.87	$168.85	$168.90
Purchase #7	$69.90	12.744%	$78.8081	$78.81	$78.80	$78.80
7 purchase totals =	$959.29		$1,041.0852	$1,041.09	$1,041.05	$1,041.10