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	$203.94	5.852%	$215.8746	$215.87	$215.85	$215.90
Purchase #2	$100.89	3.605%	$104.5271	$104.53	$104.55	$104.50
Purchase #3	$140.62	8.324%	$152.3252	$152.33	$152.35	$152.30
Purchase #4	$80.47	6.679%	$85.8446	$85.84	$85.85	$85.80
Purchase #5	$105.27	10.661%	$116.4928	$116.49	$116.50	$116.50
Purchase #6	$178.49	5.488%	$188.2855	$188.29	$188.30	$188.30
Purchase #7	$39.55	6.596%	$42.1587	$42.16	$42.15	$42.20
7 purchase totals =	$849.23		$905.5085	$905.51	$905.55	$905.50