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	$63.67	3.497%	$65.8965	$65.90	$65.90	$65.90
Purchase #2	$153.92	9.506%	$168.5516	$168.55	$168.55	$168.60
Purchase #3	$231.97	12.419%	$260.7784	$260.78	$260.80	$260.80
Purchase #4	$136.39	7.634%	$146.802	$146.80	$146.80	$146.80
Purchase #5	$235.69	13.161%	$266.7092	$266.71	$266.70	$266.70
Purchase #6	$133.62	10.470%	$147.61	$147.61	$147.60	$147.60
Purchase #7	$63.72	13.338%	$72.219	$72.22	$72.20	$72.20
7 purchase totals =	$1,018.98		$1,128.5667	$1,128.57	$1,128.55	$1,128.60