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	$47.33	12.871%	$53.4218	$53.42	$53.40	$53.40
Purchase #2	$55.34	12.675%	$62.3543	$62.35	$62.35	$62.40
Purchase #3	$143.85	7.167%	$154.1597	$154.16	$154.15	$154.20
Purchase #4	$16.85	10.171%	$18.5638	$18.56	$18.55	$18.60
Purchase #5	$144.61	11.711%	$161.5453	$161.55	$161.55	$161.50
Purchase #6	$156.63	5.734%	$165.6112	$165.61	$165.60	$165.60
Purchase #7	$113.89	11.732%	$127.2516	$127.25	$127.25	$127.30
7 purchase totals =	$678.50		$742.9077	$742.90	$742.85	$743.00