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	$55.33	11.260%	$61.5602	$61.56	$61.55	$61.60
Purchase #2	$17.53	9.644%	$19.2206	$19.22	$19.20	$19.20
Purchase #3	$29.89	11.177%	$33.2308	$33.23	$33.25	$33.20
Purchase #4	$7.45	12.586%	$8.3877	$8.39	$8.40	$8.40
Purchase #5	$126.88	9.865%	$139.3967	$139.40	$139.40	$139.40
Purchase #6	$100.67	10.659%	$111.4004	$111.40	$111.40	$111.40
Purchase #7	$192.75	5.763%	$203.8582	$203.86	$203.85	$203.90
7 purchase totals =	$530.50		$577.0546	$577.06	$577.05	$577.10