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	$59.83	10.770%	$66.2737	$66.27	$66.25	$66.30
Purchase #2	$80.84	9.220%	$88.2934	$88.29	$88.30	$88.30
Purchase #3	$112.43	9.114%	$122.6769	$122.68	$122.70	$122.70
Purchase #4	$150.25	10.662%	$166.2697	$166.27	$166.25	$166.30
Purchase #5	$89.41	10.625%	$98.9098	$98.91	$98.90	$98.90
Purchase #6	$191.48	12.354%	$215.1354	$215.14	$215.15	$215.10
Purchase #7	$118.95	7.196%	$127.5096	$127.51	$127.50	$127.50
7 purchase totals =	$803.19		$885.0685	$885.07	$885.05	$885.10