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	$193.49	11.566%	$215.8691	$215.87	$215.85	$215.90
Purchase #2	$99.90	12.352%	$112.2396	$112.24	$112.25	$112.20
Purchase #3	$146.64	6.685%	$156.4429	$156.44	$156.45	$156.40
Purchase #4	$35.43	6.261%	$37.6483	$37.65	$37.65	$37.60
Purchase #5	$60.89	9.554%	$66.7074	$66.71	$66.70	$66.70
Purchase #6	$183.77	6.284%	$195.3181	$195.32	$195.30	$195.30
Purchase #7	$159.86	7.509%	$171.8639	$171.86	$171.85	$171.90
7 purchase totals =	$879.98		$956.0893	$956.09	$956.05	$956.00