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	$181.93	12.687%	$205.0115	$205.01	$205.00	$205.00
Purchase #2	$121.58	12.514%	$136.7945	$136.79	$136.80	$136.80
Purchase #3	$90.87	9.375%	$99.3891	$99.39	$99.40	$99.40
Purchase #4	$137.77	4.261%	$143.6404	$143.64	$143.65	$143.60
Purchase #5	$112.43	12.869%	$126.8986	$126.90	$126.90	$126.90
Purchase #6	$13.40	10.831%	$14.8514	$14.85	$14.85	$14.90
Purchase #7	$136.47	10.671%	$151.0327	$151.03	$151.05	$151.00
7 purchase totals =	$794.45		$877.6182	$877.61	$877.65	$877.60