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	$77.96	10.366%	$86.0413	$86.04	$86.05	$86.00
Purchase #2	$20.83	5.301%	$21.9342	$21.93	$21.95	$21.90
Purchase #3	$237.76	3.264%	$245.5205	$245.52	$245.50	$245.50
Purchase #4	$138.88	9.851%	$152.5611	$152.56	$152.55	$152.60
Purchase #5	$41.97	11.784%	$46.9157	$46.92	$46.90	$46.90
Purchase #6	$172.94	8.277%	$187.2542	$187.25	$187.25	$187.30
Purchase #7	$93.85	10.632%	$103.8281	$103.83	$103.85	$103.80
7 purchase totals =	$784.19		$844.0551	$844.05	$844.05	$844.00