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	$63.64	12.701%	$71.7229	$71.72	$71.70	$71.70
Purchase #2	$248.50	10.618%	$274.8857	$274.89	$274.90	$274.90
Purchase #3	$38.28	12.676%	$43.1324	$43.13	$43.15	$43.10
Purchase #4	$122.86	3.417%	$127.0581	$127.06	$127.05	$127.10
Purchase #5	$10.69	10.508%	$11.8133	$11.81	$11.80	$11.80
Purchase #6	$154.47	10.472%	$170.6461	$170.65	$170.65	$170.60
Purchase #7	$68.34	11.382%	$76.1185	$76.12	$76.10	$76.10
7 purchase totals =	$706.78		$775.3770	$775.38	$775.35	$775.30