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	$63.53	6.324%	$67.5476	$67.55	$67.55	$67.50
Purchase #2	$29.48	6.381%	$31.3611	$31.36	$31.35	$31.40
Purchase #3	$37.51	10.615%	$41.4917	$41.49	$41.50	$41.50
Purchase #4	$222.64	7.522%	$239.387	$239.39	$239.40	$239.40
Purchase #5	$102.64	11.565%	$114.5103	$114.51	$114.50	$114.50
Purchase #6	$166.72	9.826%	$183.1019	$183.10	$183.10	$183.10
Purchase #7	$47.49	10.753%	$52.5966	$52.60	$52.60	$52.60
7 purchase totals =	$670.01		$729.9962	$730.00	$730.00	$730.00