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	$212.52	7.363%	$228.1678	$228.17	$228.15	$228.20
Purchase #2	$36.78	9.371%	$40.2267	$40.23	$40.25	$40.20
Purchase #3	$46.51	12.670%	$52.4028	$52.40	$52.40	$52.40
Purchase #4	$137.86	3.400%	$142.5472	$142.55	$142.55	$142.50
Purchase #5	$162.32	5.298%	$170.9197	$170.92	$170.90	$170.90
Purchase #6	$129.93	6.848%	$138.8276	$138.83	$138.85	$138.80
Purchase #7	$180.92	13.515%	$205.3713	$205.37	$205.35	$205.40
7 purchase totals =	$906.84		$978.4631	$978.47	$978.45	$978.40