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	$105.85	13.305%	$119.9333	$119.93	$119.95	$119.90
Purchase #2	$200.83	4.675%	$210.2188	$210.22	$210.20	$210.20
Purchase #3	$63.81	10.343%	$70.4099	$70.41	$70.40	$70.40
Purchase #4	$119.94	5.578%	$126.6303	$126.63	$126.65	$126.60
Purchase #5	$225.42	4.328%	$235.1762	$235.18	$235.20	$235.20
Purchase #6	$187.73	4.131%	$195.4851	$195.49	$195.50	$195.50
Purchase #7	$115.85	13.526%	$131.5199	$131.52	$131.50	$131.50
7 purchase totals =	$1,019.43		$1,089.3735	$1,089.38	$1,089.40	$1,089.30