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	$47.40	10.683%	$52.4637	$52.46	$52.45	$52.50
Purchase #2	$244.72	4.266%	$255.1598	$255.16	$255.15	$255.20
Purchase #3	$162.89	12.720%	$183.6096	$183.61	$183.60	$183.60
Purchase #4	$154.38	10.348%	$170.3552	$170.36	$170.35	$170.40
Purchase #5	$55.25	7.831%	$59.5766	$59.58	$59.60	$59.60
Purchase #6	$86.28	10.405%	$95.2574	$95.26	$95.25	$95.30
Purchase #7	$168.93	10.473%	$186.622	$186.62	$186.60	$186.60
7 purchase totals =	$919.85		$1,003.0443	$1,003.05	$1,003.00	$1,003.20