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	$59.53	9.500%	$65.1854	$65.19	$65.20	$65.20
Purchase #2	$98.70	10.396%	$108.9609	$108.96	$108.95	$109.00
Purchase #3	$130.86	8.617%	$142.1362	$142.14	$142.15	$142.10
Purchase #4	$49.81	6.762%	$53.1782	$53.18	$53.20	$53.20
Purchase #5	$5.62	3.332%	$5.8073	$5.81	$5.80	$5.80
Purchase #6	$89.89	7.716%	$96.8259	$96.83	$96.85	$96.80
Purchase #7	$89.85	11.642%	$100.3103	$100.31	$100.30	$100.30
7 purchase totals =	$524.26		$572.4042	$572.42	$572.45	$572.40