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	$168.50	11.443%	$187.7815	$187.78	$187.80	$187.80
Purchase #2	$210.48	7.694%	$226.6743	$226.67	$226.65	$226.70
Purchase #3	$166.96	9.774%	$183.2787	$183.28	$183.30	$183.30
Purchase #4	$90.29	11.797%	$100.9415	$100.94	$100.95	$100.90
Purchase #5	$145.93	8.522%	$158.3662	$158.37	$158.35	$158.40
Purchase #6	$201.29	12.238%	$225.9239	$225.92	$225.90	$225.90
Purchase #7	$57.97	13.603%	$65.8557	$65.86	$65.85	$65.90
7 purchase totals =	$1,041.42		$1,148.8218	$1,148.82	$1,148.80	$1,148.90