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	$208.91	5.278%	$219.9363	$219.94	$219.95	$219.90
Purchase #2	$207.46	7.839%	$223.7228	$223.72	$223.70	$223.70
Purchase #3	$131.75	9.749%	$144.5943	$144.59	$144.60	$144.60
Purchase #4	$131.86	4.334%	$137.5748	$137.57	$137.55	$137.60
Purchase #5	$113.58	9.580%	$124.461	$124.46	$124.45	$124.50
Purchase #6	$248.71	5.342%	$261.9961	$262.00	$262.00	$262.00
Purchase #7	$196.61	4.330%	$205.1232	$205.12	$205.10	$205.10
7 purchase totals =	$1,238.88		$1,317.4085	$1,317.40	$1,317.35	$1,317.40