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	$17.78	9.182%	$19.4126	$19.41	$19.40	$19.40
Purchase #2	$57.53	9.120%	$62.7767	$62.78	$62.80	$62.80
Purchase #3	$53.81	7.392%	$57.7876	$57.79	$57.80	$57.80
Purchase #4	$118.95	7.440%	$127.7999	$127.80	$127.80	$127.80
Purchase #5	$109.96	12.619%	$123.8359	$123.84	$123.85	$123.80
Purchase #6	$107.77	5.758%	$113.9754	$113.98	$114.00	$114.00
Purchase #7	$85.60	12.195%	$96.0389	$96.04	$96.05	$96.00
7 purchase totals =	$551.40		$601.6270	$601.64	$601.70	$601.60