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	$126.79	4.440%	$132.4195	$132.42	$132.40	$132.40
Purchase #2	$158.44	6.527%	$168.7814	$168.78	$168.80	$168.80
Purchase #3	$52.80	7.206%	$56.6048	$56.60	$56.60	$56.60
Purchase #4	$27.82	12.615%	$31.3295	$31.33	$31.35	$31.30
Purchase #5	$222.25	8.250%	$240.5856	$240.59	$240.60	$240.60
Purchase #6	$185.40	9.669%	$203.3263	$203.33	$203.35	$203.30
Purchase #7	$54.64	13.243%	$61.876	$61.88	$61.90	$61.90
7 purchase totals =	$828.14		$894.9231	$894.93	$895.00	$894.90