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	$50.32	6.575%	$53.6285	$53.63	$53.65	$53.60
Purchase #2	$15.84	9.402%	$17.3293	$17.33	$17.35	$17.30
Purchase #3	$5.25	5.391%	$5.533	$5.53	$5.55	$5.50
Purchase #4	$102.68	6.291%	$109.1396	$109.14	$109.15	$109.10
Purchase #5	$229.55	9.189%	$250.6433	$250.64	$250.65	$250.60
Purchase #6	$190.75	10.426%	$210.6376	$210.64	$210.65	$210.60
Purchase #7	$86.86	3.509%	$89.9079	$89.91	$89.90	$89.90
7 purchase totals =	$681.25		$736.8192	$736.82	$736.90	$736.60