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	$98.90	12.772%	$111.5315	$111.53	$111.55	$111.50
Purchase #2	$205.86	4.393%	$214.9034	$214.90	$214.90	$214.90
Purchase #3	$99.55	8.786%	$108.2965	$108.30	$108.30	$108.30
Purchase #4	$166.59	13.500%	$189.0797	$189.08	$189.10	$189.10
Purchase #5	$57.78	9.632%	$63.3454	$63.35	$63.35	$63.30
Purchase #6	$139.82	6.537%	$148.96	$148.96	$148.95	$149.00
Purchase #7	$156.82	13.395%	$177.826	$177.83	$177.85	$177.80
7 purchase totals =	$925.32		$1,013.9425	$1,013.95	$1,014.00	$1,013.90