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	$48.59	5.515%	$51.2697	$51.27	$51.25	$51.30
Purchase #2	$212.55	4.595%	$222.3167	$222.32	$222.30	$222.30
Purchase #3	$99.60	11.112%	$110.6676	$110.67	$110.65	$110.70
Purchase #4	$248.47	9.254%	$271.4634	$271.46	$271.45	$271.50
Purchase #5	$226.53	3.144%	$233.6521	$233.65	$233.65	$233.70
Purchase #6	$94.39	11.125%	$104.8909	$104.89	$104.90	$104.90
Purchase #7	$127.50	11.296%	$141.9024	$141.90	$141.90	$141.90
7 purchase totals =	$1,057.63		$1,136.1628	$1,136.16	$1,136.10	$1,136.30