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	$97.53	12.266%	$109.493	$109.49	$109.50	$109.50
Purchase #2	$88.32	9.319%	$96.5505	$96.55	$96.55	$96.60
Purchase #3	$222.55	6.463%	$236.9334	$236.93	$236.95	$236.90
Purchase #4	$101.83	12.242%	$114.296	$114.30	$114.30	$114.30
Purchase #5	$13.70	11.485%	$15.2734	$15.27	$15.25	$15.30
Purchase #6	$116.84	5.490%	$123.2545	$123.25	$123.25	$123.30
Purchase #7	$156.89	7.634%	$168.867	$168.87	$168.85	$168.90
7 purchase totals =	$797.66		$864.6678	$864.66	$864.65	$864.80