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	$111.85	13.631%	$127.0963	$127.10	$127.10	$127.10
Purchase #2	$5.28	3.256%	$5.4519	$5.45	$5.45	$5.50
Purchase #3	$52.32	13.326%	$59.2922	$59.29	$59.30	$59.30
Purchase #4	$63.58	12.654%	$71.6254	$71.63	$71.65	$71.60
Purchase #5	$140.60	5.243%	$147.9717	$147.97	$147.95	$148.00
Purchase #6	$210.42	6.233%	$223.5355	$223.54	$223.55	$223.50
Purchase #7	$239.48	6.734%	$255.6066	$255.61	$255.60	$255.60
7 purchase totals =	$823.53		$890.5796	$890.59	$890.60	$890.60