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	$125.70	11.143%	$139.7068	$139.71	$139.70	$139.70
Purchase #2	$92.53	7.422%	$99.3976	$99.40	$99.40	$99.40
Purchase #3	$169.96	12.613%	$191.3971	$191.40	$191.40	$191.40
Purchase #4	$52.32	3.446%	$54.1229	$54.12	$54.10	$54.10
Purchase #5	$65.67	12.622%	$73.9589	$73.96	$73.95	$74.00
Purchase #6	$73.28	11.369%	$81.6112	$81.61	$81.60	$81.60
Purchase #7	$50.94	4.493%	$53.2287	$53.23	$53.25	$53.20
7 purchase totals =	$630.40		$693.4232	$693.43	$693.40	$693.40