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	$94.53	10.112%	$104.0889	$104.09	$104.10	$104.10
Purchase #2	$166.40	11.653%	$185.7906	$185.79	$185.80	$185.80
Purchase #3	$61.80	13.617%	$70.2153	$70.22	$70.20	$70.20
Purchase #4	$247.35	13.382%	$280.4504	$280.45	$280.45	$280.50
Purchase #5	$160.57	12.406%	$180.4903	$180.49	$180.50	$180.50
Purchase #6	$92.52	10.385%	$102.1282	$102.13	$102.15	$102.10
Purchase #7	$143.38	4.653%	$150.0515	$150.05	$150.05	$150.10
7 purchase totals =	$966.55		$1,073.2152	$1,073.22	$1,073.25	$1,073.30