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	$248.89	9.530%	$272.6092	$272.61	$272.60	$272.60
Purchase #2	$208.88	9.232%	$228.1638	$228.16	$228.15	$228.20
Purchase #3	$42.59	3.660%	$44.1488	$44.15	$44.15	$44.10
Purchase #4	$168.82	11.118%	$187.5894	$187.59	$187.60	$187.60
Purchase #5	$224.26	13.554%	$254.6562	$254.66	$254.65	$254.70
Purchase #6	$66.70	5.512%	$70.3765	$70.38	$70.40	$70.40
Purchase #7	$94.55	10.476%	$104.4551	$104.46	$104.45	$104.50
7 purchase totals =	$1,054.69		$1,161.9990	$1,162.01	$1,162.00	$1,162.10