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	$38.86	11.415%	$43.2959	$43.30	$43.30	$43.30
Purchase #2	$98.94	11.759%	$110.5744	$110.57	$110.55	$110.60
Purchase #3	$182.47	7.448%	$196.0604	$196.06	$196.05	$196.10
Purchase #4	$147.65	11.636%	$164.8306	$164.83	$164.85	$164.80
Purchase #5	$76.25	10.241%	$84.0588	$84.06	$84.05	$84.10
Purchase #6	$138.60	3.743%	$143.7878	$143.79	$143.80	$143.80
Purchase #7	$79.63	13.830%	$90.6428	$90.64	$90.65	$90.60
7 purchase totals =	$762.40		$833.2507	$833.25	$833.25	$833.30