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	$123.36	3.314%	$127.4482	$127.45	$127.45	$127.40
Purchase #2	$22.70	3.411%	$23.4743	$23.47	$23.45	$23.50
Purchase #3	$50.35	9.844%	$55.3065	$55.31	$55.30	$55.30
Purchase #4	$133.83	4.200%	$139.4509	$139.45	$139.45	$139.50
Purchase #5	$127.26	11.314%	$141.6582	$141.66	$141.65	$141.70
Purchase #6	$50.56	12.194%	$56.7253	$56.73	$56.75	$56.70
Purchase #7	$172.43	7.312%	$185.0381	$185.04	$185.05	$185.00
7 purchase totals =	$680.49		$729.1015	$729.11	$729.10	$729.10