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	$61.61	9.569%	$67.5055	$67.51	$67.50	$67.50
Purchase #2	$104.41	13.217%	$118.2099	$118.21	$118.20	$118.20
Purchase #3	$82.32	10.667%	$91.1011	$91.10	$91.10	$91.10
Purchase #4	$190.65	5.121%	$200.4132	$200.41	$200.40	$200.40
Purchase #5	$177.29	12.539%	$199.5204	$199.52	$199.50	$199.50
Purchase #6	$9.58	7.180%	$10.2678	$10.27	$10.25	$10.30
Purchase #7	$5.32	13.855%	$6.0571	$6.06	$6.05	$6.10
7 purchase totals =	$631.18		$693.0750	$693.08	$693.00	$693.10