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	$95.82	10.242%	$105.6339	$105.63	$105.65	$105.60
Purchase #2	$32.39	9.539%	$35.4797	$35.48	$35.50	$35.50
Purchase #3	$111.52	10.139%	$122.827	$122.83	$122.85	$122.80
Purchase #4	$41.34	6.120%	$43.87	$43.87	$43.85	$43.90
Purchase #5	$112.74	7.665%	$121.3815	$121.38	$121.40	$121.40
Purchase #6	$96.53	3.147%	$99.5678	$99.57	$99.55	$99.60
Purchase #7	$223.55	5.580%	$236.0241	$236.02	$236.00	$236.00
7 purchase totals =	$713.89		$764.7840	$764.78	$764.80	$764.80