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	$242.91	6.745%	$259.2943	$259.29	$259.30	$259.30
Purchase #2	$82.74	7.548%	$88.9852	$88.99	$89.00	$89.00
Purchase #3	$220.45	13.209%	$249.5692	$249.57	$249.55	$249.60
Purchase #4	$144.94	13.870%	$165.0432	$165.04	$165.05	$165.00
Purchase #5	$246.65	13.781%	$280.6408	$280.64	$280.65	$280.60
Purchase #6	$55.65	11.531%	$62.067	$62.07	$62.05	$62.10
Purchase #7	$196.51	13.271%	$222.5888	$222.59	$222.60	$222.60
7 purchase totals =	$1,189.85		$1,328.1885	$1,328.19	$1,328.20	$1,328.20