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	$48.81	9.274%	$53.3366	$53.34	$53.35	$53.30
Purchase #2	$106.36	7.739%	$114.5912	$114.59	$114.60	$114.60
Purchase #3	$93.61	11.158%	$104.055	$104.06	$104.05	$104.10
Purchase #4	$123.47	3.488%	$127.7766	$127.78	$127.80	$127.80
Purchase #5	$104.82	3.497%	$108.4856	$108.49	$108.50	$108.50
Purchase #6	$196.34	8.196%	$212.432	$212.43	$212.45	$212.40
Purchase #7	$59.61	4.768%	$62.4522	$62.45	$62.45	$62.50
7 purchase totals =	$733.02		$783.1292	$783.14	$783.20	$783.20