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	$143.81	4.741%	$150.628	$150.63	$150.65	$150.60
Purchase #2	$209.25	10.371%	$230.9513	$230.95	$230.95	$231.00
Purchase #3	$187.48	4.763%	$196.4097	$196.41	$196.40	$196.40
Purchase #4	$211.27	6.420%	$224.8335	$224.83	$224.85	$224.80
Purchase #5	$114.33	11.475%	$127.4494	$127.45	$127.45	$127.40
Purchase #6	$148.59	4.726%	$155.6124	$155.61	$155.60	$155.60
Purchase #7	$202.45	9.369%	$221.4175	$221.42	$221.40	$221.40
7 purchase totals =	$1,217.18		$1,307.3018	$1,307.30	$1,307.30	$1,307.20