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	$29.52	10.218%	$32.5364	$32.54	$32.55	$32.50
Purchase #2	$86.93	3.868%	$90.2925	$90.29	$90.30	$90.30
Purchase #3	$174.73	9.494%	$191.3189	$191.32	$191.30	$191.30
Purchase #4	$74.64	3.443%	$77.2099	$77.21	$77.20	$77.20
Purchase #5	$92.60	5.191%	$97.4069	$97.41	$97.40	$97.40
Purchase #6	$168.35	7.790%	$181.4645	$181.46	$181.45	$181.50
Purchase #7	$48.60	8.686%	$52.8214	$52.82	$52.80	$52.80
7 purchase totals =	$675.37		$723.0505	$723.05	$723.00	$723.00