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	$153.96	9.433%	$168.483	$168.48	$168.50	$168.50
Purchase #2	$68.73	12.795%	$77.524	$77.52	$77.50	$77.50
Purchase #3	$54.40	12.195%	$61.0341	$61.03	$61.05	$61.00
Purchase #4	$101.84	9.757%	$111.7765	$111.78	$111.80	$111.80
Purchase #5	$49.42	11.736%	$55.2199	$55.22	$55.20	$55.20
Purchase #6	$179.32	5.561%	$189.292	$189.29	$189.30	$189.30
Purchase #7	$247.26	10.523%	$273.2792	$273.28	$273.30	$273.30
7 purchase totals =	$854.93		$936.6087	$936.60	$936.65	$936.60