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	$83.27	9.862%	$91.4821	$91.48	$91.50	$91.50
Purchase #2	$143.74	6.665%	$153.3203	$153.32	$153.30	$153.30
Purchase #3	$75.28	4.533%	$78.6924	$78.69	$78.70	$78.70
Purchase #4	$217.62	7.804%	$234.6031	$234.60	$234.60	$234.60
Purchase #5	$173.97	12.693%	$196.052	$196.05	$196.05	$196.10
Purchase #6	$28.86	5.493%	$30.4453	$30.45	$30.45	$30.40
Purchase #7	$222.65	6.856%	$237.9149	$237.91	$237.90	$237.90
7 purchase totals =	$945.39		$1,022.5101	$1,022.50	$1,022.50	$1,022.50