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	$47.88	10.856%	$53.0779	$53.08	$53.10	$53.10
Purchase #2	$68.78	6.772%	$73.4378	$73.44	$73.45	$73.40
Purchase #3	$222.53	13.801%	$253.2414	$253.24	$253.25	$253.20
Purchase #4	$97.76	8.195%	$105.7714	$105.77	$105.75	$105.80
Purchase #5	$38.42	11.377%	$42.791	$42.79	$42.80	$42.80
Purchase #6	$28.95	6.558%	$30.8485	$30.85	$30.85	$30.80
Purchase #7	$123.50	11.103%	$137.2122	$137.21	$137.20	$137.20
7 purchase totals =	$627.82		$696.3802	$696.38	$696.40	$696.30