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	$61.72	6.768%	$65.8972	$65.90	$65.90	$65.90
Purchase #2	$131.77	11.256%	$146.602	$146.60	$146.60	$146.60
Purchase #3	$240.68	12.708%	$271.2656	$271.27	$271.25	$271.30
Purchase #4	$249.85	3.663%	$259.002	$259.00	$259.00	$259.00
Purchase #5	$228.89	13.156%	$259.0028	$259.00	$259.00	$259.00
Purchase #6	$139.30	11.168%	$154.857	$154.86	$154.85	$154.90
Purchase #7	$225.66	10.310%	$248.9255	$248.93	$248.95	$248.90
7 purchase totals =	$1,277.87		$1,405.5521	$1,405.56	$1,405.55	$1,405.60