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	$29.81	7.855%	$32.1516	$32.15	$32.15	$32.20
Purchase #2	$122.50	6.260%	$130.1685	$130.17	$130.15	$130.20
Purchase #3	$38.49	12.811%	$43.421	$43.42	$43.40	$43.40
Purchase #4	$181.25	3.675%	$187.9109	$187.91	$187.90	$187.90
Purchase #5	$109.88	3.832%	$114.0906	$114.09	$114.10	$114.10
Purchase #6	$89.45	3.509%	$92.5888	$92.59	$92.60	$92.60
Purchase #7	$24.53	11.247%	$27.2889	$27.29	$27.30	$27.30
7 purchase totals =	$595.91		$627.6203	$627.62	$627.60	$627.70