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	$41.50	9.601%	$45.4844	$45.48	$45.50	$45.50
Purchase #2	$137.55	6.632%	$146.6723	$146.67	$146.65	$146.70
Purchase #3	$125.91	13.225%	$142.5616	$142.56	$142.55	$142.60
Purchase #4	$131.71	4.131%	$137.1509	$137.15	$137.15	$137.20
Purchase #5	$200.26	7.573%	$215.4257	$215.43	$215.45	$215.40
Purchase #6	$60.68	5.370%	$63.9385	$63.94	$63.95	$63.90
Purchase #7	$115.32	6.727%	$123.0776	$123.08	$123.10	$123.10
7 purchase totals =	$812.93		$874.3110	$874.31	$874.35	$874.40