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	$95.83	10.182%	$105.5874	$105.59	$105.60	$105.60
Purchase #2	$57.38	12.689%	$64.6609	$64.66	$64.65	$64.70
Purchase #3	$81.71	8.725%	$88.8392	$88.84	$88.85	$88.80
Purchase #4	$86.45	11.223%	$96.1523	$96.15	$96.15	$96.20
Purchase #5	$192.82	11.301%	$214.6106	$214.61	$214.60	$214.60
Purchase #6	$73.87	6.174%	$78.4307	$78.43	$78.45	$78.40
Purchase #7	$114.68	4.693%	$120.0619	$120.06	$120.05	$120.10
7 purchase totals =	$702.74		$768.3430	$768.34	$768.35	$768.40