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	$54.71	13.734%	$62.2239	$62.22	$62.20	$62.20
Purchase #2	$7.84	8.509%	$8.5071	$8.51	$8.50	$8.50
Purchase #3	$85.32	6.122%	$90.5433	$90.54	$90.55	$90.50
Purchase #4	$231.27	12.446%	$260.0539	$260.05	$260.05	$260.10
Purchase #5	$156.28	3.718%	$162.0905	$162.09	$162.10	$162.10
Purchase #6	$76.89	4.865%	$80.6307	$80.63	$80.65	$80.60
Purchase #7	$49.47	3.745%	$51.3227	$51.32	$51.30	$51.30
7 purchase totals =	$661.78		$715.3721	$715.36	$715.35	$715.30