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	$47.61	9.276%	$52.0263	$52.03	$52.05	$52.00
Purchase #2	$242.30	12.726%	$273.1351	$273.14	$273.15	$273.10
Purchase #3	$118.78	3.140%	$122.5097	$122.51	$122.50	$122.50
Purchase #4	$140.77	13.591%	$159.9021	$159.90	$159.90	$159.90
Purchase #5	$189.69	13.625%	$215.5353	$215.54	$215.55	$215.50
Purchase #6	$174.54	7.678%	$187.9412	$187.94	$187.95	$187.90
Purchase #7	$81.53	13.455%	$92.4999	$92.50	$92.50	$92.50
7 purchase totals =	$995.22		$1,103.5496	$1,103.56	$1,103.60	$1,103.40