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	$78.94	13.515%	$89.6087	$89.61	$89.60	$89.60
Purchase #2	$15.32	3.366%	$15.8357	$15.84	$15.85	$15.80
Purchase #3	$185.65	10.763%	$205.6315	$205.63	$205.65	$205.60
Purchase #4	$219.41	6.216%	$233.0485	$233.05	$233.05	$233.00
Purchase #5	$142.29	4.274%	$148.3715	$148.37	$148.35	$148.40
Purchase #6	$38.40	6.499%	$40.8956	$40.90	$40.90	$40.90
Purchase #7	$5.60	13.328%	$6.3464	$6.35	$6.35	$6.30
7 purchase totals =	$685.61		$739.7379	$739.75	$739.75	$739.60