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	$237.86	5.364%	$250.6188	$250.62	$250.60	$250.60
Purchase #2	$18.29	13.438%	$20.7478	$20.75	$20.75	$20.70
Purchase #3	$72.95	12.759%	$82.2577	$82.26	$82.25	$82.30
Purchase #4	$56.94	11.372%	$63.4152	$63.42	$63.40	$63.40
Purchase #5	$111.84	7.685%	$120.4349	$120.43	$120.45	$120.40
Purchase #6	$200.29	5.651%	$211.6084	$211.61	$211.60	$211.60
Purchase #7	$12.31	12.296%	$13.8236	$13.82	$13.80	$13.80
7 purchase totals =	$710.48		$762.9064	$762.91	$762.85	$762.80