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	$49.28	10.657%	$54.5318	$54.53	$54.55	$54.50
Purchase #2	$167.79	6.169%	$178.141	$178.14	$178.15	$178.10
Purchase #3	$172.93	13.623%	$196.4883	$196.49	$196.50	$196.50
Purchase #4	$119.31	11.644%	$133.2025	$133.20	$133.20	$133.20
Purchase #5	$104.71	9.643%	$114.8072	$114.81	$114.80	$114.80
Purchase #6	$73.86	5.746%	$78.104	$78.10	$78.10	$78.10
Purchase #7	$161.34	8.122%	$174.444	$174.44	$174.45	$174.40
7 purchase totals =	$849.22		$929.7188	$929.71	$929.75	$929.60